Here's how I did this problem.
Alberts hair is already 5 centimetres long. We know that his hair grows by 4 centimetres every year, and we have to figure out how long it takes until his hair is 33 centimetres. So, it's easier to subtract 33 from 5, and see if that result is divisible by 4, and it is, because 33-5 is 28, which goes into 4, 7 times. (4*7 = 28), so it will take Albert 7 years, until his hair is 33 centimetres long.
Hope this helped.
