Question 789772
angle 1 = x
angle 2 = x + 12

x + (x + 12) = 90
2x + 12 = 90
2x + 12 - 12 + 90 - 12
2x = 78
2x/2 = 78/2
x = 39

check:
39 + (39 + 12) = 90
39 + 51 = 90
90 = 90