For Road 1, the car travels at a rate of 60 miles in 2 hours. We can write this as the equation:
$$\frac{60}{2} = \frac{y}{x}$$
For Road 2, the car travels at a rate of 90 miles in 4 hours. We can write this as the equation:
$$\frac{90}{4} = \frac{y}{x}$$
Since we want to represent the motion of the faster car, we will use the equation for Road 2, which yields:
$$\frac{90}{4} = \frac{y}{x}$$