work backwards
x5/2 + 1 = 3 so x = 4
x4/2 + 1 = 4 so x4 = 6
work it 3 more times to find x1, the starting amount
Jeff took half of the marbles out of the bag. He then put 1 marble back into the bag. He repeated this process five times. There were 3 marbles left in the bag at the end. How many marbles were there in the bag at first?
1 answer