There are y horses and z chickens in a barn. How many legs are there in the barn?

There are y horses and z chickens in a barn. How many legs are there in the barn?

For total legs, we have:
Total Legs = Horse Legs + Chicken Legs
Total Legs = Legs per horse * number of horses + Legs per chicken * number of chickens

Horses have 4 legs and chickens have 2 legs. We have y horses and z chickens. Plugging this in, we have:
Total Legs = 4y + 2z