Today, a tank contains 6,600 gallons of water. For the past three days, 210 gallons of water was pumped out of the tank each day. What was the volume of the water in the tank three days ago

answer:

c. the third graph

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

a

step-by-step explanation: