You can multiply 7*6=42. That is all i can think of at this moment. I will improve the answer if i come up with more.
How about: 2 times 21 = 42
Multiply 42 times 12=504 inches
420
2 when multiplied by 21 = 42
2*21 = 42
42
42
42
Because you can't multiply 9 by an integer to get 42.
multiply 4 and 42, then you have your aswer.
You would get 42
42