1)
(3x + y) + (x + 4y + 2) = 90
4x + 5y + 2 = 90
4x + 5y = 88
2)
(x + 4y + 2) + (3y - 3) = 90
x + 7y - 1 = 90
x = 91 - 7y
substitute eq(2) into eq(1):
4(91 - 7y) + 5y = 88
364 - 28y + 5y = 88
276 = 23y
y = 276/23 = 12 degrees
using eq(2):
x = 91 - 7(12)
x = 7 degrees
check using eq(1):
4(7) + 5(12) = 88
28 + 60 = 88