Additional Arithmetic Rules: Applying the formula

$100-(30-21)=$

According to the order of operations, we first solve the exercise within parentheses:

$30-21=9$

Now we obtain:

$100-9=91$

$91$

$13-(7+4)=$

According to the order of operations, we first solve the exercise within parentheses:

$7+4=11$

Now we subtract:

$13-11=2$

$2$

$12:(2\times2)=$

According to the order of operations, we first solve the exercise within parentheses:

$2\times2=4$

Now we divide:

$12:4=3$

$3$

$55-(8+21)=$

According to the order of operations, we first solve the exercise within parentheses:

$8+21=29$

Now we obtain the exercise:

$55-29=26$

$26$

$60:(5\times3)=$

We write the exercise in fraction form:

$\frac{60}{5\times3}$

We break down 60 into a multiplication exercise:

$\frac{20\times3}{5\times3}=$

We simplify the 3s and obtain:

$\frac{20}{5}$

We break down the 5 into a multiplication exercise:

$\frac{5\times4}{5}=$

We simplify the 5 and obtain:

$\frac{4}{1}=4$

$4$

$60:(10\times2)=$

We write the exercise in fraction form:

$\frac{60}{10\times2}=$

Let's separate the numerator into a multiplication exercise:

$\frac{10\times6}{10\times2}=$

We simplify the 10 in the numerator and denominator, obtaining:

$\frac{6}{2}=3$

$3$

$28-(4+9)=$

According to the order of operations, we first solve the exercise within parentheses:

$4+9=13$

Now we obtain the exercise:

$28-13=15$

$15$

$37-(4-7)=$

According to the order of operations, we first solve the exercise within parentheses:

$4-7=-3$

Now we obtain:

$37-(-3)=$

Remember that the product of a negative and a negative results in a positive, therefore:

$-(-3)=+3$

Now we obtain:

$37+3=40$

$40$

$22-(28-3)=$

According to the order of operations, we first solve the exercise within parentheses:

$28-3=25$

Now we obtain the exercise:

$22-25=-3$

$-3$

$38-(18+20)=$

According to the order of operations, first we solve the exercise within parentheses:

$18+20=38$

Now, the exercise obtained is:

$38-38=0$

$0$

$7-(4+2)=$

According to the order of operations, we first solve the exercise within parentheses:

$4+2=6$

Now we solve the rest of the exercise:

$7-6=1$

$1$

$8-(2+1)=$

According to the order of operations, we first solve the exercise within parentheses:

$2+1=3$

Now we solve the rest of the exercise:

$8-3=5$

$5$

$66-(15-10)=$

According to the order of operations rules, we first solve the expression inside of the parentheses:

$15-10=5$

We obtain the following expression:

$66-5=61$

$61$

$80-(4-12)=$

According to the order of operations, we first solve the exercise within parentheses:

$4-12=-8$

Now we obtain the exercise:

$80-(-8)=$

Remember that the product of plus and plus gives us a positive:

$-(-8)=+8$

Now we obtain:

$80+8=88$

$88$

$5-(13-8)=$

According to the order of operations, we first solve the exercise within parentheses:

$13-8=5$

Now we obtain the exercise:

$5-5=0$

$0$

$80:(4\times2)=$

According to the order of operations, we first solve the exercise within parentheses:

$4\times2=8$

Now we divide:

$80:8=10$

$10$

$35:(2\times7)=$

We write the exercise in fraction form:

$\frac{35}{2\times7}=$

We separate the numerator into a multiplication exercise:

$\frac{7\times5}{2\times7}=$

We simplify the 7 in the numerator and denominator, obtaining:

$\frac{5}{2}=2\frac{1}{2}$

$2\frac{1}{2}$

$9:(3\times2)=$

We rewrite the expression as a fraction:

$\frac{9}{3\times2}=$

We rewrite the numerator as a multiplication expression:

$\frac{3\times3}{3\times2}=$

We simplify the 3 in the numerator and denominator, obtaining:

$\frac{3}{2}=1\frac{1}{2}=1.5$

$1.5$

$-33-(17-3)=$

According to the order of operations, we first solve the exercise within parentheses:

$17-3=14$

Now we obtain the exercise:

$-33-14=-47$

$-47$

$49-(53-18)=$

According to the order of operations, we first solve the exercise within parentheses:

$53-18=35$

We obtain the exercise:

$49-35=14$

$14$