The total charge C for a rental that includes insurance can be found by adding the standard charge S and the insurance charge I:
C = S + I
Substituting the given expressions for S and I, we get:
C = (0.60M + 16.95) + (0.25M + 5.80)
Simplifying and combining like terms, we get:
C = 0.85M + 22.75
Therefore, the equation relating C to M is:
C = 0.85M + 22.75
This equation shows that the total charge C for a rental that includes insurance is a linear function of the number of miles driven M, with a slope of 0.85 and a y-intercept of 22.75.