These questions are essentially of the form total=100 * number / percentage. Your are given two parts of this equation. In this case you were given percentage and number and you are asked to compute the total. You needed to multiply number by 100 and then divide by percentage to calculate the correct answer.

You have 29 boxes. You have 65% of the total number of boxes. How many boxes total are there?

t=29%*100/65
t=2900/65
t=44