Find the point of intersection between y=2-(1/2)x and y=1+ax. (a=alpha sign). You answer will be a point in the xy plane whose coordinates involve the unknown a .

I got that which is
x=2/(2a+1), y=(1+2a)/(2a+1) <-intersection point

I need help is to: Find a (a=alpha sign) so that the intersection point has x-coordinate 10. How do I do this?

You've done the hard part; you're almost there! You just lost sight of the simple bit.

x = 2/(2a+1)

we need to find a when x = 10

10 = 2/(2a+1)

Now find a