y varies directly as x, and y = - 72
when x = 6, solve for y when x = 3
varies directly as
varies directly as means
y = kx where k is a constant
xk = y
Plugging in y = - 72 when x = 6
-72 = 6k
Divide each side by 6
| 6k | |
| 6 |
| = |
| -72 |
| 6 |
Cancel the 6 on the left side
| = |
| -72 |
| 6 |
Plug in k = -12
y = -12x
We were given that x = 3
y = -12(3)
Final Answer
y = -36
