He paid 20 + 13, so 33 for the pumpkins and now you need to add the tax.
To compute the TAX ONLY, you would multiply 0.07 ( which is 7%) by 33, and you get $2.31. So the final cost with tax would be $33+ $2.31= $35.31
An easier way to compute total cost with the tax included would be to multiply $33 by 1.07, and you get the same answer as above, $35.31.
Do you see the difference? Some questions will ask for the amount of tax only, others will ask for the amount paid including tax.
