5 - (2 over 7)d = 3
$\displaystyle 5-\frac{2}{7d}=3$....subtracting 5 from both sides you get[tex]\frac{-2}{7d}=-2[/MATh]...now by divding by a negative you get[tex]\frac{2}{7d}=2[/MATh] multiplying by 7d you get $\displaystyle 2=14d$...and then by dividing by 14 you get $\displaystyle d=1/7$