Question 1017981
<pre>
If x:y:z = a:b:c

Then

{{{x/(x+y+z)=a/(a+b+c)}}}, {{{y/(x+y+z)=b/(a+b+c)}}}, {{{z/(x+y+z)=c/(a+b+c)}}}


Let the number of chickens be x
Let the number of lambs be y
Let the number of cows be z
a:b:c = 1:2:4
x+y+z = 21
a+b+c = 1+2+4 = 7

{{{x/(21)=1/(7)}}}, {{{y/(21)=2/(7)}}}, {{{z/(21)=4/(7)}}}

Multiply each through by 21

{{{x=3}}}, {{{y=6}}}, {{{z=12}}}

Edwin</pre>