Addition and subtraction: Solving the problem

According to the order of operations, we will solve the exercise from left to right since the only operations in it are addition and subtraction:

$90-2=88$

$88+9=97$

$97-8=89$

Due to the fact that the exercise only involves addition and subtraction operations, we will solve it from left to right:

$14-5=9$

$9-9=0$

$0+7=7$

$7+2=9$

Due to the fact that the exercise only involves addition and subtraction operations, we will solve it from left to right:

$26-6=20$

$20+9=29$

$29+7=36$

$36-12=24$

Due to the fact that the exercise only involves addition and subtraction operations, we will solve it from left to right:

$32-4=28$

$28-19=9$

$9+3=12$

$12-7=5$

Insofar as the exercise only involves addition and subtraction operations, we will solve it from left to right:

$30+6=36$

$36-5=31$

$31+7=38$

$38-17=21$