If a house has the proper amount of insulation, how many degrees cooler should the home be inside without any a/c? If it is 96° outside, what would you expect the temp to be inside with no a/c or windows open. thanks.

Way, way to many other factors involved to even make a guess.
Time of day, location of home in relationship to the sun.
Venting.
Humidity.
Landscaping, ECT.
Why are you asking?

The short story is that you need the A/C, even with good insulation. Beyond that there is no way to answer your question. As Joe says, too many variables.

Last week I had to work in a small ranch style house that is empty, There's no curtins, no over head trees, all the windows were closed, no A/C runing.
It was 90 deg. plus outside, on the inside it was only 75 deg.
I go home that night to a closed up house will all the curtins closed and it's 80 deg. inside with no A/C.

Thanks for all replies.

A closed up house (well insulated) is going to be slow to both warm up and cool down. So if it is just sitting through the week closed, it will not be able to cool off at night (no open windows to allow cooler air in, and built up heat out).

Insulation translates to temperature "Resistance"...thus the R-factor, listed on the different types/thicknesses.