ive seen this puzzle going about for quite a while now but havent been able to solve it yet , anybody got any ideas? , its called: 'Sum Sums' and is laid out below as it exactly appears:-

THIRTY-SIX MINUS TEN =

3 + 3 + 3 x 3 =

5 x 5 x 0 =

20 - 15 =

Add the numbers!