This expression is correct. It shows the price John pays for the jeans on the left side of the + symbol (30n), and the amount of tax he has to pay on the right side of the symbol (0.08(30n)).
Hope this helps!
The inequality would start out looking like this:

Now it's just a matter of solving the inequalities simultaneously. Get rid of the fraction by multiplying everything by 9:

Then distribute the 5 into the parenthesis:

Now add 160 everywhere:

and finally divide everything by 5:
-22<F<266