alternate interior angles means the angles across from another are equal. If you follow the line up 85 is directly across from 2x+1
then you can say
85 = 2x +1
85 -1 = 2x
84 = 2x
84/2 = x
42 = x
supplementary angles make a straight line so they must add to equal 180 degrees.
That means the other angle 3y+5 = 180-85
3y +5 = 95
3y = 95-5
3y = 90
y = 90/3
y = 30
