Solve (90-15-3)÷8: Step-by-Step Expression Evaluation

Fraction Evaluation with Sequential Subtraction

90−15−38= \frac{90-15-3}{8}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve the following expression
00:04 Calculate the numerator and then proceed to divide
00:08 Solve the expression according to the proper order of operations from left to right
00:13 Each time we must calculate one operation and then continue
00:24 Break down 72 into factors 9 and 8
00:27 Reduce wherever possible
00:30 Here is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

90−15−38= \frac{90-15-3}{8}=

2

Step-by-step solution

Let's begin by solving the numerator of the fraction from left to right, according to the order of operations:

90−15=75 90-15=75

75−3=72 75-3=72

We should obtain the following exercise:

728=72:8=9 \frac{72}{8}=72:8=9

3

Final Answer

9 9

Key Points to Remember

Essential concepts to master this topic
  • Order of Operations: Solve numerator completely before dividing by denominator
  • Technique: Calculate 90 - 15 = 75, then 75 - 3 = 72
  • Check: Verify 9 × 8 = 72 matches our numerator ✓

Common Mistakes

Avoid these frequent errors
  • Dividing before completing numerator operations
    Don't divide 90 by 8 first = 11.25 - 15 - 3 gives wrong negative result! This breaks order of operations and creates impossible calculations. Always complete all numerator operations first, then divide the final result.

Practice Quiz

Test your knowledge with interactive questions

\( 100+5-100+5 \)

FAQ

Everything you need to know about this question

Why can't I just divide each number by 8 separately?

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Because the fraction bar acts like parentheses - you must solve the entire numerator first! Dividing each term separately changes the mathematical meaning completely.

What if I accidentally get a decimal answer?

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Check your arithmetic! This problem should give you a whole number. If you get decimals, you likely divided too early or made a calculation error.

How do I remember the order of operations with fractions?

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Think of the fraction bar as a grouping symbol. Just like with parentheses, solve everything above the line first, then divide by what's below.

Can I rewrite this as (90-15-3)÷8?

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Yes! 90−15−38 \frac{90-15-3}{8} is exactly the same as (90-15-3)÷8. Both mean: solve the subtraction first, then divide by 8.

What's the fastest way to check my answer?

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Multiply your answer by the denominator: 9×8=72 9 \times 8 = 72 . This should equal your calculated numerator!

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