Let's say the number of days library book is late is X, and the total fee is Y.
Liability charges $0.30 dollars as a fee for being 1 day late,
For being 1 day late, fee charge is: 1* $0.30 So, for X days the charge would be: X*$0.30.
Total charge for being X days late is Y, Which means: Y= 0.30 * X.
Now We would have to check all the viable solutions in the answer to see if they satisfy the equation Y= 0.30 * X
Option one(-3, -0.9) and two (-2.5, -0.75) Would not be a viable solution because the value of number of days can not be negative and in option one and two, value of days -3 and -2.5 is negative.
Option three(4.5, 1.35) can not be correct because library charges fee for a full day so the number for days would be a whole number. Library would not charge for 4.5 days, they would either charge of 4 days or 5 days because 4.5 is not an whole number.
Option four(8, 2.40) is the correct answer because it satisfies our equation;
Y= 0.30 * X
2.40= 0.30 * 8
2.40 = 2.40.
Fourth option (8, 2.40) is the only viable solution to this question.
