Question

A lending library has a fixed charge for the first $3$ days and an additional charge for each day thereafter..... Sarita paid $Rs27$ for a book kept for $7$ days while Susy paid $Rs21$ for the book she kept for $5$ days. Find the fixed charge and charge for each extra day.

Answer 1

Let the fixed charge be $a$

Let the additional be $b$

From the given conditions

$a+4d=27$

$a+2d=21$

$⟹d=3,a=15$