How to calculate percentage of a number. Use the percentage formula: P% * X = Y
Convert the problem to an equation using the percentage formula: P% * X = Y.
P is 10%, X is 150, so the equation is 10% * 150 = Y.
Convert 10% to a decimal by removing the percent sign and dividing by 100: 10/100 = 0.10.
By iteratively substituting, we have



and the pattern continues down to the first term
,



Recall the formulas


It follows that



Answer:
casey's age is 7
Step-by-step explanation:
if his sister is 3 times as old as he is then she is older therefore you would devide.
21/3=7