since this is an isosceles triangle
5x =40
divide by 5
x=8
the sum of all angles in a triangle is 180
5x+40 + 2y+20 = 180
substitute 40 in for 5x
40 + 40 + 2y+20 = 180
combine like terms
100 + 2y = 180
subtract 100 from each side
2y = 80
divide by 2
y= 40
