how do you add a regular function to a fraction function

I don't know what you mean.  Perhaps you could provide us with an example?

Perhaps you mean something like  7x+(x/8)?

If you want to make it all one term then you need a comon denominator which will be 8

So it will become

$$7x+\frac{x}{8}\\\\
=\frac{7*8x}{8}+\frac{x}{8}\\\\
=\frac{56x+x}{8}\\\\
=\frac{57x}{8}\\\\$$