Question 26883
Then you've done the hard part... most people have trouble translating from english to math, but you're doing fine so far. Just need to solve the system of equations.
{{{a-b=16}}}
{{{3a=7b}}}
The easiest way for this particular problem is substitution, solving the first equation for a you get:
{{{a=16+b}}} When you put that into equation 2...
{{{3(16+b)=7b}}}
Distribute: {{{48+3b=7b}}}
Rearrange: {{{48=4b}}}
Solve: {{{12=b}}}
Substituting in for equation 1:
{{{a-12=16}}}
{{{a=28}}}

Double check: {{{3*28=84}}}{{{7*12=84}}} check.