algebra
posted by marc .
A 3mi cab ride costs $3.00. A 6mi cab ride costs $4.80. Find a linear equation that models cost c as a function of distance d. write your linear equation using function notation.

c = f(d) = m d + b
3 = m (3) + b
4.8 = m (6) + b
subtract
1.8 = 3m
m = 1.8/3 = .6
find b
3 = .6 (3) +b
b = .4(3) = 1.2
so
c = .6 d + 1.2