At first you may get confused but look at those numbers carefully :)
as you see first result is divisible buy one of the product (second product in all cases is unknown)
so let's check where it will lead us :)
\(6/2=3\)
\(12/3=4\)
\(20/4=5\)
\(30/5=6\)
\(42/6=7\)
Now you can clearly see that every number was multiplied by number 1 higher than itself.
\(2*(2+1)=6\)
\(3*(3+1)=12\)
\(4*(4+1)=20\)
etc...
it means that after equation sign there should be \(90\) because
\(9*(9+1)=90\) :)
