Pls help I’m timed. It’s for my unit test

What is the missing constant term in the perfect square that starts with x^2 -20x

Tamera puts 15/4 gallons of gasoline in her car. which mixed number represents the gallons of gasoline? a) 2 3/4 gallons b) 3 1/4 gallons c) 3 3/4 gallons d) 4 1/2 gallons answer it's worth a lot of points!

Find the value of x. round the length to the nearest tenth