Question

The farm animals have been sorted into cows and chickens. The number of chickens is two less than five times the number of cows. The animals are 80% chickens. How many cows are there?

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Answer 1

let x = # of chickens and y = # of cows

The number of chickens is two less than five times the number of cows. ---> x = 5y - 2
The animals are 80% chickens. ---> the total # of animals is x + y, so 80% of all animals would be 0.8(x + y). if 80% are chickens, x = 0.8(x+y)

there's a couple ways you could do this, but I'd personally distribute 0.8 across the parentheses in the second equation, simplify, get x on one side only. then, you have two equations both solved for x in terms of y and you can simply set them equal to each other. once you have x, the number of chickens, you can easily solve for y, the number of cows, by plugging back into either equation.