so, parallel lines have the same slope, therefore a parallel line to 2x+12, will have the same slope as that one, so which is it? [tex]\bf y=\stackrel{slope}{2}x\stackrel{y-intercept}{+12}[/tex]
so, we're really looking for the equation of a line whose slope is 2, and runs through -1,1.
[tex]\bf \begin{array}{lllll}
&x_1&y_1\\
% (a,b)
&({{ -1}}\quad ,&{{ 1}})
\end{array}
\\\\\\
% slope = m
slope = {{ m}}= \cfrac{rise}{run} \implies 2
\\\\\\
% point-slope intercept
\stackrel{\textit{point-slope form}}{y-{{ y_1}}={{ m}}(x-{{ x_1}})}\implies y-1=2[x-(-1)]
\\\\\\
y-1=2(x+1)\implies y-1=2x+2\implies y=2x+3[/tex]