Since it's a constant amount, divide $4.50 by 3 to get $1.50 each.

This also works for $13.50; divide $13.50 by 9 to get $1.50.

To check your answers: is 1 x $1.50 = $3.00? If not, what should it be?

Also: is 5 x $1.50 = $7.50?

And is 8 x $1.50 = $6.00?