Question 1059597
The average of all 3 numbers is {{{(a+b+c)/3}}} .
The average of {{{a}}} and {{{b}}} is {{{(a+b)/2}}} .
The problem says that
{{{(1/2)*((a+b+c)/3)=2*((a+b)/2)}}}
which simplifies to
{{{(a+b+c)/6=a+b}}} .
Multiplying both sides of the equal sign times {{{6}}} . we get the equivalent equation
{{{a+b+c=6(a+b)}}}
Subtracting {{{(a+b)}}} from both sides of the equal sign we get
{{{c=6(a+b)-(a+b)}}} , which simplifies to
{{{highlight(c=5(a+b))}}} .