Pat kept track of the number of hours that he spent at the park each week for several weeks. He spent 10, 4, 1, and 5 hours. What is the mean number of hours that Pat spent at the park each week? O A. 20 hours O B. 9 hours O C. 5 hours O D. 4 hours​

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