Question 1039627
Clara is 2/3 as old as Liz;<pre>{{{C=expr(2/3)L}}}

Multiply both sides by 3 to clear the fraction

(1)   {{{3C=2L}}}</pre>Maria is 1/6 as old as Clara<pre>{{{M=expr(1/6)C}}}

Multiply both sides by 6 to clear the fraction

(2)   {{{6M=C}}}

Use (2) to substitute 6M for C in (1):

{{{3(6M)=2L}}}

{{{18M=2L}}}

(3)   {{{9M=L}}}</pre>Liz is younger than 21<pre>{{{L<21}}}

Use (3) to substitute 9M for L

{{{9M<21}}}
{{{M<21/9}}}
{{{M<7/3}}}
{{{M<2&1/3}}}

So Maria is either 1 or 2

If Maria were only 1, then, substituting
M=1 in (2)   

{{{6(1)=C}}}
{{{6=C}}}

But</pre>Clara is in the sixth grade<pre>So she can't be only 6.
So Maria must be 2

(4)   M=2

substituting M=2 in (2)   

{{{6(2)=C}}}
{{{12=C}}}

Normally one is only 11 in the sixth grade, but
Clara could have failed a grade. So Maria is 2,
and Clara is 12.</pre>how old is she (Liz)?<pre>Using (4) to substitute 2 for M in (3)

{{{9M=L}}}

{{{9(2)=L}}}

{{{18=L}}}

Liz is 18.

Edwin</pre></b>