Let C is the number of coins Casey has <span>Andrew has seven fewer coins than casey = C - 7 </span><span>Bob has three more than twice as many coins as Andrew = 2(C-7) + 3 </span>altogether, they have 502 coins = C + (C - 7) + 2(C-7) + 3 = 502
Now solve for C: C + (C - 7) + 2(C-7) + 3 = 502 C + C - 7 + 2C - 14 + 3 = 502 4C - 18 = 502 4C = 502 + 18 4C = 520 C =520/4 C = 130