Question 1143215
The sum of their ages is:
{{{ b + ( b + 4 ) = 2b + 4 }}}
---------------------------------
Check:
suppose her brother is 10
Then Jonna is {{{ 10 + 4 = 14 }}}
The sum of their ages is {{{ 10 + 14 = 24 }}}
and
{{{ 2b + 4 = 2*10 + 4 }}}
{{{ 2*10 + 4 = 24 }}}
OK