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4-99.

CHANGING POPULATIONS Homework Help ✎

Highland has a population of 12,200. Its population has been increasing at a rate of 300 people per year. Lowville has a population of 21,000 but is declining by 250 people per year. Assuming these rates do not change, in how many years will the populations be equal?

Write an equation that represents each city's population over time. What do your variables represent?

Solve the problem. Show your work.

How do the current populations and rates of change relate to *y* = *mx + b*?

The rate of change is the slope.

Highland: *y* = 300*x* + 12,100

Lowville: *y* = −250*x* + 21,000

Be sure to identify what the variable represent.

Use the Equal Values Method.