Suppose that Sahil knows that 45 people with the ages of 18 to 19 voted. With out using a calculator, he quickly says then 135 people with the ages of 30 to 49 voted. Is he correct? How might shail have come up with his answer?

( I have a chart and one thing that is a clue is that the ages 18 to 29 is 10% )
(Ages 30 to 49 is 30%) please help!

I know that he did 45 times 3 to get the 135 because he though since 10% is 45 people he could multiply by 3 & get his answer. Help!!!