1. 3x=18

Question

2. 25x=50
3. 115+118+81+(2x+8)=360

Answer 1

if 3 x = 18
divide both sides by 3

similarly if 25 x = 50
divide both sides by 25

115 + 118 + 81 + 8 = 322
so
2 x + 322 = 360
subtract 322 from both sides
2 x = 38
divide both sides by 2