Answer:
x = 39
Step-by-step explanation:
The sum of the 3 angles in a triangle = 180° , then
x + x + 12 + 90 = 180
2x + 102 = 180 ( subtract 102 from both sides )
2x = 78 ( divide both sides by 2 )
Then
x = 39°
x + 12 = 39 + 12 = 51°
