What is the value of y?

This triangle is isosceles   with  AB  = AC  ....so....the angles opposite these sides are also =

So  angle   (5x)°  = 40...so these two angles sum to 80°

So...this means that    2y + 20  must = 100

So

2y =  80

So....y  =  40

The sum of angles in a triangle adds up to 180 degrees. So we can subtract 60 to get 120 = 5x + 2y. Now we need to solve for y. Y is on the same side of the equation as x, so we need to move the x by subtracting 5x. Then we have 2y = 120 - 5x. Last, we need to divide by 2, as that is the coefficient of y. Now, we have y = 60 - 2.5x.

OK.....I'll have to think a bit about that....!!!!!!