Question 984512
Let Sue's age be given by S
Let Beth's age be given by B. You are told {{{B = 3S}}}
Let Jill's age be given by J. You are told {{{J = 2S}}}

You are also told the sum of their ages is 30
So {{{30 = S + B + J}}}
Substituting from the first set of equations, we get
{{{30 = S + 3S + 2S}}}
{{{30 = 6S}}}
{{{5 = S}}}

So Sue is 5, Beth is 15 and Jill is 10