$x + y = 7 $and $x^3 - y^3 = 37$, find $xy$ 
$x+y=7$
  $x^3-y^3 = 37$
Find $xy$

I have tackled this one but I am stuck, when I get to this point:
$$(x-y)((x+2)^2 -xy) = 37$$
I would be glad if you could give me any suggestions.

$(49-4xy)(49-xy)^2=37^2$
, $37$ is prime. So $49-4xy=1$ then
$$xy=12$$
