solve for y
a(y+c)=b(y-c)
solve for w
a=lw+wh+lh

I am pretty sure that the solution I attach below is the correct one :

And what about the next part of your task, the answer is : 

Do hope you will find it useful!

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .