Anne sold 20 gallons of lemonade. Carol sold 10 fewer quarts. How many quarts did carol sell?

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

Answer for 10 points show work you guys in advanced < 3

What is the length of the segment, endpoints of which are intersections of parabolas y=x^2− 11/4 x− 7/4 and y=− 7 /8 x^2+x+ 31/8 ?