Answer:
x=5
Step-by-step explanation:
The sum of the angles of a triangle are 180 degrees
The box is a right angle which is 90 degrees
60+6x+90 = 180
Combine like terms
150+6x= 180
Subtract 150 from each side
150-150+6x = 180-150
6x = 30
Divide by 6
6x/6 =30/6
x = 5
