To find the inverse function, interchange the variables and solve for y.
f^-1(n) = 1/2 + n/3
If you divide 8 into 4 you would get 2. The four numbers are 2,4,6 and 8. So there are 6. Hope that helps you good luck.
If c is the hypotenuse and b is the leg, then the third side (a):

If b and с are legs, then hypotenuse (a):