Question 103168
You want to end up with an equation that looks like {{{d=...}}} so you must move all d terms over to one side 
and all non-d terms over to the other side. 
{{{-d/7 = -13 }}}
{{{(-d/7)*(-7) = -13*(-7)}}} Use the multiplicative inverse of (-1/7) or (-7) since {{{(-1/7)*(-7)=1.}}} 
Remember what you do to one side of the equation you must do to the other side. 
{{{d*(-1/7)*(-7)=91}}} Expand since {{{a*b*c = (a*b)*c}}}
{{{d*(1)=91}}}
{{{d=91}}}