2 hours
First find the equation for car 2.
Difference in y/ difference in X = gradient.
20/1 = 20
Find the y intercept where x = 0.
y intercept = 40
Equation: y = 20x + 40
Use simultaneous equations to find the point at which they're the same distance.
Equate the equations.
30x + 20 = 20x + 40
Out it into the formula Ax = b so you have all the X's on one side and all the integers on the other.
30x + 20 - 20x = 20x + 40 - 20x
10x +20 = 40
10x + 20 - 20 = 40 - 20
10x = 20
10x / 10 = 20 / 10
x = 2
2 hours will pass.
Substitute X for 2 to check it's correct.
30x + 20 = 30 * 2 + 20 = 60 + 20 = 80
20x + 40 = 20 * 2 + 40 = 40 + 40 = 80
