$ The Farm Puzzle 
$
$ A farmer has 7 animals on his farm: pigs and hens.
$ They all together have 22 legs. How many pigs (4 legs)
$ and how many hens(2 legs) does the farmer have?
$
$ modelled by Karen Petrie

language ESSENCE' 1.b.a

find pigs, hens: int(0..7)

such that
     pigs*4 + 2*hens = 22,
     pigs + hens = 7