Problem referred below

Suppose that sahil knows that 45 people with ages of 18 to 29 voted. without using a calculator, he quickly says then 135 people with ages of 30to 49 voted. is he correct? how might sohil have come up with his answer so quickly?

Adele is five years older than timothy. in three years, timothy will be 2/3 of adele’s age. what is adele‘s current age?

If twice a number is at least three less than four times the number, which of the following are true? let n represent the number.