<PRE><B>Question 1173938</B>
&lt;br&gt;
The solution from the other tutor sets up the proportion as&lt;br&gt;
{{{21/3 = x/4}}}&lt;br&gt;
and solves that equation (proportion) to find x=28.&lt;br&gt;
That is of course valid.  However, the problem is more easily solved by setting up the proportion as&lt;br&gt;
{{{3/4 = 21/x}}}&lt;br&gt;
Then the problem is solved by looking at these as equivalent fractions; since 21 is 7 times 3, x has to be 7 times 4, or 28.&lt;br&gt;
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Note to tutor @ikleyn --&lt;br&gt;
There is currently a typo in your response (21/7 instead of 21/3)&lt;br&gt;
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