A small rural town has experienced a population decrease at a rate of 25 people every 5 years since 1970. If the population of the town in 1970 was 250, which of the following equations represents the town’s population as a function of time? (Assume 1970 is represented by x = 0, 1971 is represented by x = 1, and so on).

I am absolutely terrible when it comes to math!

Question

A small rural town has experienced a population decrease at a rate of 25 people every 5 years since 1970. If the population of the town in 1970 was 250, which of the following equations represents the town’s population as a function of time? (Assume 1970 is represented by x = 0, 1971 is represented by x = 1, and so on).

I am absolutely terrible when it comes to math!

anonymous · Answer

Forgot to add the answer choices :/ 
A.
y = –5x + 250
B.
y = –25x + 250
C.
–5x + y = 250
D.
–x – 25y = 250

ranga · Answer

Here y is the population and x is the year since 1970.

They tell you that the "population decreases at the rate of 25 people every 5 years"

slope of a line = difference in y / difference in x (or rise / run) = -25 / 5
slope m = -5   

when x = 0 (that is the year 1970), the population is 250.  
x = 0 represents the y-intercept.

So which answer choice has slope = -5 and y-intercept = 250 ?