Respuesta :
-- So it gains 3.5 m/s of speed every second.
-- In 11 sec, it'll gain (3.5 x 11) = 38.5 m/s of speed.
-- Added to its original speed of 15 m/s,
it'll then be moving at (15 + 38.5) = 53.5 m/s .
There's no information in the question regarding the direction of motion
at any time, so there's no way to say anything about velocity.
I also got 53.5 m :) final velocity = initial velocity + acceleration x time