This month Jane walked a total distance of 36 miles. If this distance is 90% of the distance she walked last month, how much distance did Jane walk last month?
This month Jane walked a fraction of the distance she walked last month, 36 miles is part of a whole. To get the whole, you first have to turn the percentage into a decimal.
90% = 90/100
We then divide the part by the decimal in the last step to get the whole.
As a way of checking, you can divide 36 by 40 and take note of the decimal you get.
36/40 = 0.9, which tells us that our answer is correct.
Jane walked 40 miles last month.