Question 339207
There is enough hay for 4 cows for 3 weeks. First
find out many weeks worth of hay there is for 1 cow.
half as many cows can last twice as long on the same 
amount of hay, so
There is enough hay for 2 cows for 6 weeks.
There is enough hay for 1 cow for 12 weeks.
There is enough hay for {{{x}}} cows for {{{12/x}}} weeks -answer
So, if there were {{{12}}} cows,
There is enough hay for {{{x = 12}}} cows for {{{12/12 = 1}}} week.