We can use the formula:

v = u + at

where:

v = final velocity = 7.5 m/s

u = initial velocity = 0 m/s (car is starting from rest)

a = acceleration = 15 m/s²

t = time taken

We can rearrange the formula to solve for t:

t = (v - u) / a

Substituting the given values:

t = (7.5 m/s - 0 m/s) / 15 m/s²

t = 0.5 seconds

Therefore, the car will take 0.5 seconds to reach a final speed of 7.5 m/s.