Answer:25$
Step-by-step explanation: 21$ is 84% of how much money Cho had last month. So we need to find 100%. You can use a proportion which makes it easier to solve in my opinion. The proportion is 21 over x = 84/100. x is the amount of money Cho had last month which we don't know. 84/100 is 84% out of 100% since any percent is always out of 100. If we cross-multiply and make the proportion into an equation. The equation: 84*x=21*100 which simplifies into 84x=2100. If you do 2100/84, you would get 25 which is x which is the amount of money Cho had last month.