20 got 4 added to it and the only number that gives you 24 when you multiply it is 4x6 and we can prove that to be right because the one before it is 4x5 and it gives us 20. Now that we know the multiplier is 5 and 6 we can ask ourselves, "What do I multiply by 5 that gives me 60?" And that is 12. So 12x6 is 72 for x.
