(9+10=21) (step 1) First we find the two numbers whose product is equal 9 (3x3) and we find the two numbers whose product is equalvilant to 10 (5x2). (step 2) Now we put the eqations next each other 5x2 3x3 and multiply them starting from the middle outwards (2x3=6) (5x3=15). (step three) Now we add those answers (15+6) and the answer comes out to be 21.
