let be the years since 1990. and we write our points as

we have the point since in 1990 (when t = 0) the life expectancy (f(t)) was 78.8

and the point by a similar reasoning.

now we simply need to find the equation of the line that passes through these two points.

the slope is given by:

and we can find the line using the point slope form:

here is one of the points the line passes through. plug in the values and solve for (which is )

you can answer this once you have the answer to the last question. this is just asking for f(18)b. Use this function to estimate the life expectancy of females in 2008

If some one could please help me I would be sooooo greatful