What is the final velocity of a runner who is accelerating at 2 feet per second squared for 3 second with an initial velocity of 4 feet per second

He starts at a speed of 4 fps.

He adds 2 fps of speed during each of 3 seconds, for a gain of 6 fps.

At the end of the 3 sec, his speed is (4 + 6) = 10 fps.

We know nothing about the direction in which he runs, so we're in no position to discuss velocity. The best we can do is to determine his final speed.

The answer for this is 9/1253decimal form 0.007

Could you make it more clear?