Question

Careful measurements have been made of Olympic sprinters in the 100-meter dash. A simple but reasonably accurate model is that a sprinter accelerates at 3.4 m/s2 for 3.30 s, then runs at constant velocity to the finish line.

Answer 1

In problem makes two statements but does not ask any questions. But ...

Sprinter starts from rest and accelerate at 3.4 m/s^2 for 3.30 s.
u = 0
a = 3.4 m/s^2
t = 3.3 s
v = ?

v = u + at = 0 + 3.4 * 3.3 = 11.22 m/s

So the sprinter accelerates to the speed of 11.22 m/s after which the sprinter runs at constant velocity to the finish line.

Not knowing the question hopefully the answer is contained above.