Question 268253
Let m represetn mathews age today and j represent jenny's age today
Given
{{{m = 3j}}}
{{{m+7 = 2(j+7)}}}
{{{m+7 = 2j+14}}}
Substitute from the first equation
{{{3j + 7 = 2j+14}}}
{{{j = 7}}}
So Jenny is 7
That makes Matthew 3*7  =21