Question

The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May her driving cost was $370 for 720 mi and in June her cost was $410 for 800 mi. Assume that there is a linear relationship between the monthly cost C of driving a car and the distance driven d.

Find a linear equation that relates C and d.

Answer 1

You need an equation for C in terms of d, and you have to points (d,C): (720,370) and (800,410).
The point form of a linear equation is (in terms of x and y:
\[y - y _{1} = \frac{ y _{2} - y _{1} }{ x _{2} - x _{1} }(x - x _{1)}\]
This is when you have an equation of y in terms of x, and points (x1, y1) and (x2, y2).
Here use C instead of y, d instead of x, and for the two points, use (720, 370) and (800, 410) for (x1, y1) and (x2, y2)

Answer 2

@mathstudent55 thank you so much!