Find the value of X.

As you see this is a right angle, so the sum of the two angles = 90°

So,

(x + 42) + 3x = 90°

Remove the parentheses:

x + 42 + 3x = 90

Combine like terms:

4x + 42 = 90

Subtract 42 on both sides:

4x = 48

Divide 4 on both sides:

x = 12

~