Answer: 2x+1
Notice how the 2x in the answer and the x, from x+6, multiplies to 2x^2
Also the 1 from the answer and the 6 from x+6 multiplies to 6
The results of 2x^2 and 6 are the first and last terms respectively of the original trinomial. None of the other answer choices fit this.
You can use the FOIL or box method to get
(x+6)*(2x+1) = x*(2x+1)+6*(2x+1)
(x+6)*(2x+1) = 2x^2+x+12x+6
(x+6)*(2x+1) = 2x^2+13x+6
which confirms the answer is 2x+1