So, all you would do is use distribution.
For example: D is .5(x+3) = -3(x-.5)
you would do
.5 times x+3, which equals .5x+ 1.5
So, .5x+1.5=-3x+1.5
because -3*x-.5 is -3x+1.5.
Then, you would just get x by itself.
.5x+1.5=-3x+1.5
add 3 over to .5 = 3.5x;
subtract 1.5 over to 1.5 = 0
now you have 3.5x = 0
divide by 3.5 to get x by itself and you get zero.
x=0
When you substitute it in, you should have them both equal to each other. I hope this helps. :)