Question 1002578
j, g, d, for Jake, Grandpa, Dad



Examining the description very carefully, you should be able to form this system of equations:
{{{system(j=13,g+3=2(d+3),g+7=4(j+7))}}}


One of the variables is already given as known, so you can substitute for it now and you will have a system of two equations, just in the unknown variables, g and d.


{{{system(g+3=2d+6,g+7=4j+28)}}}


{{{system(g=2d+3,g=4j+21)}}}


{{{system(g=2d+3,g=4*13+21)}}}


{{{system(2d=g-3,g=52+21)}}}


{{{highlight(g=73)}}}---------Grandpa;
but still you want to know d, from the other equation in the last system;


{{{2d=g-3}}}
{{{2d=73-3}}}
{{{d=70/2}}}
{{{highlight(highlight(d=35))}}}-----------Jake's dad.