How do i cross multiply if the variable is on the right fractions top? example: 7/8 = x/12

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!

What is the image of c for a 90° counterclockwise rotation about a? (3, 7) (-1, 3) (7, 3)

An arithmetic series a consists of consecutive integers that are multiples of 4 what is the sum of the first 9 terms of this sequence if the first term is 0