For a car moving at a constant speed, the distance traveled varies directly with the time spent driving. If such a car travels 225 miles in 3 hours, how many miles does it travel in 7 hours? \( \square \) miles

Step 1 ：\(d = k \cdot t\)

Step 2 ：\(225 = k \cdot 3\)

Step 3 ：\(k = \frac{225}{3} = 75\)

Step 4 ：\(d = 75 \cdot 7 = 525\)

Step 5 ：\( \square \) miles