Find two positive numbers where the sum of the first and twice the second is 90

We have two numbers called a and b. And remember a, positive
But you have to add these numbers are whole numbers
We have a+2xb=90
Notice that a is an even number and less than 90. So we have so many solution like (a=2, b=44), (a=4, b=43)(a=88, b=1)
So we have 45 solutions.
Notice that if these numbers are not whole number, so we have an infinitive of solution