The common difference is 12.
I take it that only 7 stamps are misplaced and that we are asked for the total value of the stamps including those which have been misplaced.
If each is worth $0.15 then, the total worth of 7 stamps is $1.05. Then, we add this value to the value of his remaining stamps, $5.55, the answer would be $6.60.
Answer: 20
Step-by-step explanation:
Given
The cost of an individual ticket is $25
The cost of a couple's ticket is $40
The total sale is $2500
total ticket sold is 70
Suppose there are x individuals and y couples


So, they sold 20 tickets of the individual.