[PICTURE ATTACHED] Solve the equation: 14w = 91. I don’t know what this means because i’ve never learned it in my class. Could someone care to explain what it means and whats the answer? :D

At the "no mutants allowed" country farm, every sheep has 4 legs, every chicken has two legs, and all animals have only 1 head. asked to count how many sheep and chicken are in the fields, a farm boy reports back that there are 140 feet and 50 heads. how many sheep and chicken are there? there are sheep and chicken at the farm.