How to solve an equation of this type (screenshot)?

Question

Mathematics

I'm bad at math, I'm asking for help, I can only just substitute and count, but I get a negative answer, can't the speed be negative?
Screenshot:

Answer 1

The speed, like the coordinate, can be negative. Only time can be positive.

Answer 2

you can take the derivative of the given equation: x' = v = t/3 + 1
v(3) = 3/3 + 1 = 2 m/s
In addition to the answer, I would advise you to read about the physical meaning of the derivative