Answer
12. x = 15, y = 21
13. x = 10, M = 37, N = 84, P =59
14. x = 19, R = 43, S = 20, T = 117
15. A = 21, B = 125, C = 34
16. J = 48, K = 57, L = 75
Explanation
12. 6x - 11 + x + 5 + 81 = 180
7x + 75 = 180
7x = 105
x = 15
4y - 18 + y + 14 + 6*15 - 11 = 180
5y + 75 = 180
5y = 105
y = 21
13. 4x - 3 + 9x - 6 + 6x - 1 = 180
19x - 10 = 180
19x = 190
x = 10
M = 4*10 - 3 = 37
N = 9*10 - 6 = 84
P = 6*10 - 1 = 59
14. R = 2x + 5
S = x + 1
T = 7x - 16
2x + 5 + x + 1 + 7x - 16 = 180
10x - 10 = 180
10x = 190
x = 19
R = 2*19 + 5 = 43
S = 19 + 1 = 20
T = 7*19 -16
15. A = C -13
B = 4C - 11
c - 13 + 4c - 11 + c = 180
6c -24 = 180
6c = 2-4
C = 34
A = 34 - 13 = 21
B = 4*34 - 11 = 125
16. K = J + 9
L = 2J -21
j + 9 + 2j - 21 + j = 180
4j -12 = 180
4j = 192
J = 48
K = 48 + 9 = 57
L = 2*48 -21 = 75
