What is the missing constant term in the perfect square that starts with x^2-16x

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

What is the effect on the graph of the function f(x)=x when f(x) is replaced with -f(x)+4

Examine this system of equations. what integer should the second equation be multiplied by so that when the two equations are added together, the x term is eliminated? 3/4x+1/7y=6 1/8x-3/5y=16