13. 5y + 10 = 6y - 2....vertical angles are equal
5y - 6y = -2 - 10
-y = - 12
y = 12 <==
2x + 40 = 110...vertical angles are equal
2x = 110 - 40
2x = 70
x = 70/2
x = 35 <==
====================
14. x = 0.5x + 17.5....vertical angles are equal
x - 0.5x = 17.5
0.5x = 17.5
x = 17.5 / 0.5
x = 35 <==
y = 145 <== vertical angles are congruent
================
15. x + 42 = 52
x = 52 - 42
x = 10 <==
6y + 8 = 7y - 12
6y - 7y = -12 - 8
- y = -20
y = 20 <==
==================
16. 75 + 4y + 25 = 180.....supplementary angles = 180
4y + 100 = 180
4y = 180 - 100
4y = 80
y = 80/4
y = 20 <==
75 + 2x - 5 = 180...supplementary angles = 180
2x + 70 = 180
2x = 180 - 70
2x = 110
x = 110/2
x = 55 <==
==================
17. 3y + 13 + 5y - 1 = 180...supplementary angles = 180
8y + 12 = 180
8y = 180 - 12
8y = 168
y = 168/8
y = 21 <==
11x + 16 + 8x + 12 = 180
19x + 28 = 180
19x = 180 - 28
19x = 152
x = 152/19
x = 8 <==
==================
18. 3x + 17 = 5x - 47...vertical angles are equal
3x - 5x = -47 - 17
-2x = - 64
x = -64/-2
x = 32 <==
2y + 9 = 3y - 20
2y - 3y = -20 - 9
-y = -29
y = 29 <==