Help plz my teacher didn't explain how i'm supposed to solve these

See below for each answer. I did it step by step.

Step-by-step explanation:

90=(x+18)+x 90-18=x+x 90-18=2x 72=2x x=36

90=(x-52)+x 90+52=2x 142=2x x=71

180=(x-10)+(x-20)+x 180+10+20=3x. 190+20=3x 210=3x x=70

90=(x+36)+x 90-36=2x 54=2x x=26

90=(x+10)+(x+10) 90-10-10=2x 80-10=2x 70=2x x=35

180=(x+20)+x 180-20=2x 160=2x x=80

180=(x-14)+x 180+14=2x 194=2x x=97

180=(x+20)+(x+10) 180-20-10=2x 160-10=2x 150=2x x=75

the answer is the third / last answer

step-by-step explanation:

50-60=10

step-by-step explanation: