Answer
3y = 120$^{\circ}$
(y - 15) = 25$^{\circ}$
Work Step by Step
All angles in a triangle must add up to 180∘. We can therefore add the three given angle measures together, set them equal to 180∘, and then solve for y.
35 + 3y + (y-15) = 180
35 - 35 + 3y + (y-15) = 180 - 35
3y + (y-15) = 145
(We can re-write (y-15) as y - 15.)
3y + y - 15 = 145
3y + y - 15 + 15 = 145 + 15
3y + y = 160
We can now combine like-terms and then solve for y.
4y = 160
4y = 160
y = 40$^{\circ}$
We can now solve for each individual angle measure.
The angle labelled 3y really equals (3 x 40) = 120$^{\circ}$.
The angle labelled (y - 15) really equals (40 - 15) = 25$^{\circ}$.
