Answer
The solution $(-2,14)$ is not a viable solution because it is not possible to have time be -2 hours. So, the tanks never have the same amount of water.
Work Step by Step
Let x = the number of hours the tanks are leaking and let y = the amount of water left in the tank.
The first tank contains 10 gal of water and is leaking at a constant rate of 2 gal/h: $y=10-2x$
The second tank contains 6 gal of water and is leaking at a constant rate of 4 gal/h: $y=6-4x$
Using substitution to solve the equation:
$6-4x=10-2x$
$2x=-4$
$x=-2$
Substitute -2 for x in either equation and solve for y.
$y=10-2(-2)=14$
The solution $(-2,14)$ is not a viable solution because it is not possible to have time be -2 hours. So, the tanks never have the same amount of water.