We shall use the formula
v² = u² + 2as
where
v = final speed. v = 0 because the cyclist comes to a complete stop.
u = initial speed. u = 11 m/s, given
a = acceleration. a = -3.0 m/s², given
s = distance traveled, m.
Therefore
0 = 11² + 2(-3.0)*s
0 = 121 - 6s
That is,
6s = 121
s = 121/6 = 20.167 m
Answer: 20.2 m (nearest tenth)