11. The two angles are vertical angles, which mean they are equal to each other.
14x - 5 = 13x
Add 5 to both sides:
14x = 13x + 5
Subtract 13x from both sides:
x = 5
12. The two angles are supplementary and when added together need to equal 180 degrees.
5x -20 + 3x = 180
Combine like terms:
8x -20 = 180
Add 20 to both sides:
8x = 200
Divide both sides by 8:
x = 200 /8
x = 25