Question 1109438
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You can't have fractional numbers of birds, so the other tutor's answer is clearly not right.  In fact he got the wrong answer by using 18 as the total number of birds, instead of the number of bluebirds.<br>
Here are a couple of different solution methods....<br>
using ratio and proportion...
The ratio of bluebirds to parakeets is 2:3 = 18:x.  So 2x = 18*3 = 54; x = 27.<br>
also using ratio and proportion but showing the ratios as fractions...
{{{2/3 = 18/x}}}
{{{2x = 18*3}}}  ["cross multiply"]
{{{2x = 54}}}
{{{x = 27}}}<br>
using algebra...
To represent the ratio of 2 to 3, let the number or bluebirds be 2x and the number of parakeets be 3x.  Then since the number of bluebirds is 18,
{{{2x = 18}}}
{{{x = 9}}}
The number of parakeets is 3x = 27.