Just let

As for your work...

You cannot split fractions in this way. is not, in general, equal to

Also, you are integrating from 8 to 10, not 10 to 8 (unless you wrote it wrong at the top of your post).

Okay, even if we assume that your previous work was correct, this line does not make sense. You can only apply the power rule...

2 + 1/6 [((e^(-90+1))/(-90+1)) - ((e^(-72+1))/(-72+1))]when the variable is not in the exponent.For an exponential function like you need to use the following rules.

If the base is something other than you can use