The answer you want is 90, but the way you wrote the question sucks. 2 = 6, but 6 = 42. Which means that 2 = 42. Now what the hell are we supposed to make of that?

It can also be interpreted as (n*n)+n, or as n*n+n so... 2*2+2 = 6 3*3+3 = 12 4*4+4 = 20 5*5+5 = 30 6*6+6 = 42 therefore: 9*9+9=90