Change in speed = (final speed) - (initial speed) = 10-26 = -16
Divide this over the change in time (2 seconds) to get -16/2 = -8
The negative indicates we're slowing down or that the velocity is decreasing.
The direction of the acceleration is opposite of the car's movement, so the direction of acceleration (or more accurately deceleration) is east.
In summary:
Magnitude = 8 m/s^2
direction = east
