calculation – How to solve \$ lim_ {n to infty} overset {n} sum_ {k = 1} 3 (1+ frac {2k} {n}) frac {2} {n} \$?

I need to solve $$lim_ {n to infty} overset {n} sum_ {k = 1} 3 (1+ frac {2k} {n}) frac {2} {n}$$

I've worked on that by trying to compute $$int ^ 3_ {1} 3xdx$$but I do not know how to get rid of the k and find the closed form of the equation.

$$Delta x = frac {b-a} {n} = frac {2} {n}$$

$$x_ {k} = a + Delta x_ {k} = 1 + frac {2_ {k}} {N}$$