Iwill mark brainiest , if correct. .

You would need to buy 14 gallons of paint.

If you really want to figure this out you make an equation to solve for the time
let's let
x = time from Elena to Jada and
x = time from Jada to Elena
12 then the equation
12 = 5x +3x
would help figuring out their distance say for one of them
12 = x(5+3)
12/8 = x
1.5 = x
1. 5 hours they will meet up