To do this, I'd create an equation.
here's what we're given:
- the total angle is 90 degrees
-one part of the angle is 2x
- the other part is 3x + 15
So you could pretty much make this an addition sequence:
2x + 3x + 15= 90
combine like terms
5x + 15= 90
5x=90-15
5x= 75
x= 15
now you know x, so substitute x=15 into the two expressions for the measurements of the angles
1) 2(15)= 30
2) 3(15) + 15= 60
and you know this is correct because if you add the two answers together, you get 90 !!!
hope this makes sense :)