The Pham family and the Jenkins family each used their sprinklers last summer. The water output rate for the Pham family's sprinkler was 15 L per hour. The water output rate for the Jenkins family's sprinkler was 30 L per hour. The families used their sprinklers for a combined total of 50 hours, resulting in a total water output of 975 L. How long was each sprinkler used?
Use Substitution to solve
-4x+3y=-13
Y=3x-6
X=
Y=