Question 1190140


let Berto’s age be {{{B}}} and Joana’s age {{{J}}}

if Berto is {{{5}}} years older than Joana, we have

{{{B=J+5}}}......eq.1

if three years ago, the sum of their ages is {{{21}}}, we have

{{{(B-3)+(J-3)=21}}}
{{{B+J-6=21}}}
{{{B+J=21+6}}}
{{{B+J=27}}}..........substitute  {{{B}}} from eq.1

{{{J+5+J=27}}}
{{{2J=27-5}}}
{{{2J=22}}}
{{{J=11}}}

go to

{{{B=J+5}}}......eq.1, ..substitute  {{{J}}}
{{{B=11+5}}}
{{{B=16}}}

Berto is {{{16}}} and Joana is {{{11}}} now.