Harold took 5 hours to paint 3 same-sized walls. If he works at the same rate, how long will it take him to paint 18 walls of the same size?

30 hours

Step-by-step explanation:

We can use ratios to solve

5 hours        x hours

=

3 walls          18 walls

Using cross products

5*18 = 3x

Divide each side by 3

5*18/3 = 3x/3

30 =x

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

answer: all of the odd numbers were opened

the first person was the one that was opening all of the lockers. since one is odd, this causes all of the odd number lockers to be opened in the end.