If f (x) = (3+x) / (x-3) what is f (a+2)

To answer items such as this, we directly substitute the a + 2 to the all the x's in the function such that,

f (a + 2) = (3 + a + 2) / (a + 2 - 3)

Simplifying the function generated above,

f (a + 2) = (5 + a) / (a - 1)