I can't understand this solution. Question asks for the span of $\{v_1,v_2\}$, given $v_1 = (2,3), v_2= (4,6)$.
I follow until the solution says: $$\operatorname{span}\{v_1,v_2\}=\{(c+2d)(2,3) \mid c,d \in \mathbb{R}\}.$$
Then it goes $=\{e(2,3) \mid e \in \mathbb{R}\}.$
I don't understand how $c+2d = e$?