How many two digit numbers are divisible by either 3 or 5?

There are 18 that are divisible by 5. 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95

now find which of those are divisible by 3 (divide the numbers by three and if its a whole number that works for example 30 divided by 3 is 10 so thats one) 

There are 30 two digit numbers divisible by 3, and all two digit numbers are divisible by 5

Xis -1/2
y is 35/4.