A box of 6kg is pulled to the right on horizontal surface by force of 20 N. The box experience a constant friction force of 3N during it's motion

3 answers

20 - 3 = m a
17 = 6 a
a = 17 / 6
So what is the question? This seems to be the day for half worded questions.
What was its initial speed? How long to accelerate to whatever speed? Distance during acceleration?
Calculate normal force.
The normal force on the ground is m g = 6 * 9.81 Newtons