You'd have no problem simplifying that expression if it said
-(5 cows) - (1 cow) + ( 14 cows) - (3 cows) .
You'd just add up the cows, and simplify the expression to say
5 cows .
When you see an expression that talks about 'x's instead of cows, you get scared. It has something to do with algebra and math and all that stuff, so you freeze.
Relax. Just make each 'x' a cow, and suddenly it almost solves itself.
So we know 5% is 1/20 out of 100 (20x5=100) so then we need to set up the equation to find how much 5% of 15 is. Which is .75 cents. So we then add the 75 cents to the already $15 shipping fee to get an answer of 15 dollars and seventy five cents.