A - 24!
-21 as its true value is 21
-3 as its true value is 3
if you add them together you get 24!
Hope this helped ^^
You need to expand (4x-7)(x+3), multiplying each term in the first bracket by each term in the second bracket, in order to get 4x^2+5x-21. Hope that helps!
When you're out shopping and something you want to buy is on sale. You can take the original price and give it's percentage to find out how much it really is.