Question

The Zonda Information and Telephone Company (ZI&T) calculates a customer’s total monthly cell phone

charge using the formula,
C = (b + rm)(1 + t),
where C is the total cell phone charge, b is a basic monthly fee, r is the rate per minute, m is the number
of minutes used that month, and t is the tax rate.
Solve for m, the number of minutes the customer used that month.

Answer 1

The answer of the following question is m = \frac{C - b - bt}{r + rt}.

Solution:

C = (b + rm)(1 + t),

C = b + rm + bt + rmt

C = b + bt + rm + rmt

C - b - bt = m (r + rt)

\frac{C - b - bt}{r + rt} = m

t\\eq -1,

r\\eq 0