Question

$18:[(5^2 - 5x)*2 - 11]=2$

Answer 1

18/[[25-5x]·2-11]=2
⇒50-10x-11=18/2
⇒50-10x-11=9
⇒50-10x=11+9
⇒50-10x=20
⇒10x=50-20
⇒10x=30
⇒x=30/10
⇒x=3;

Answer 2

( 25  - 5x ) · 2  - 11  = 18 :2
50  - 10·x  - 11 = 9
39  - 10·x = 9
39  -9 = 10·x 
10·x = 30 
x = 30 /10 = 3