In october, greg and thomas had the same amount of money in their savings accounts. in november, greg deposited $120 into his account. thomas increased the money in his account by 20%. when they compared their balances, they found that they were still equal. how much money did they both have in their accounts in october?

If Greg deposited $120 into his account and Thomas increased his money by 20% and they still got the same amount in November, it means that $120 is 20% of their money in October.

120 = 20% * x (where x is the money in October)
120 = 20/100x
120 = 2/10x
120 = 1/5x            / * 5 (both sides)
x = 600

So each of them had $600 in October.

Doublecheck:

Greg's money = 600 + 120 = 720
Thomas' money = 600 + 20% * 600 = 600 + 120 = 720

So it's correct :)