1) V = a × t, where v is the velocity, a is the acceleration and t is the time
2) Vf - Vi = a × t
So 1.3 - 1.1 = a × 20
a = 0.01 m/s²
3) Vf - Vi = a × t
0 - 2 = a × 3
a = -2/3 m/s²
4) If an object is slowing down, the acceleration is negative and vice versa.