x = 37.5 (or) 
Solution:
Given 
AC = 50, DE = 30, EC = 25, BE = x, BC = 25 + x
To find the value of x:
Property of similar triangles:
If two triangles are similar then the corresponding angles are congruent and the corresponding sides are in proportion.


Do cross multiplication, we get


Subtract 30x from both sides of the equation.

Divide by 20 on both sides of the equation, we get
x = 37.5 (or) 
Hence the value of x is 37.5 or
.
This are the right steps
Step 1: first you divide the both size by 7 because there is 7 a's
7a/7 = 28/7
Step 2: You solve the equation
7a/7= a. 28/7 = 4
So, the answer is a = 4
not 7 = 4
The expression is Undefined for x=0, assuming you intend 1/(-8x).
x=0 is "nonpermissible"
7x = -36+10x
X=12
You minus the 10 from 7 (7-10=-3) (-36/-3) gives you 12