2/3 of a right triangle is 60 degrees. Then x + (x+20) + 60 = 180 total.
2x + 80 = 180, so 2x = 100 and x = 50. The angles are 50, 70 and 60 (degrees)
What do you mean by "grades?"
recall from the previous posting, 2⁸ = 256, so that's one way to represent it.
now, another way hmmm

8.7 The absolute value just makes stuff positive.
Answer:
x=20 degrees
Step-by-step explanation:
complementary means the angles equal 90 degrees
so ∠A+∠B=90 degrees
∠A=3x-2 and ∠B=x+12
so subsitute
(3x-2)+(x+12)=90
then solve for x
4x+10=90
4x=80
x=20 degrees is your answer