6x + 5 + 4x + 5 = 90
x = 8
Explanation:
The square/box in red represent angle 90 degrees.
This means the sum of angles in it is 90 degrees
The equation:
6x + 5 + 4x + 5 = 90 (sum of angles in a right angle)
simplify by collecting like terms:
6x + 4x = 5 + 5 = 90
10x + 10 = 90
subtract 10 from both sides:
10x + 10 - 10 = 90 - 10
10x + 0 = 80
10x = 80
divide both sides by 10;
10x/10 = 80/10
x = 8
