#### Answer

Particle A
v = -10 m/s
Particle B
v = -20 m/s
Particle C
v = 75 m/s

#### Work Step by Step

Particle A
The velocity will be equal to the slope of the position versus time graph.
$v = \frac{-60~m}{6~s}$
$v = -10~m/s$
Particle B
We can read the velocity directly from the graph.
$v = -20~m/s$
Particle C
The change of velocity will be equal to the area under the acceleration versus time graph.
$\Delta v = 65~m/s$
$v = v_0+\Delta v$
$v = 10~m/s + 65~m/s$
$v = 75~m/s$