Question 497324
16x - 4 + 2x + 13 = 90 degrees.
18x + 9 = 90 degrees.
18x = 81
x = 4.5
16(4.5) - 4 = 68 degrees.
2(4.5) + 13 = 22 degrees.  
68 + 22 = 90 degrees. This does check.
Cleomenius.