A photographer studio charges a sitting fee of $50 and $10 per enlargement ordered. Write an equation to represent the number of enlargements ordered, n , by a customer if the total cost was $180. Then find the number the number of enlargements ordered.**Solution:**

If n is the number of enlargements ordered, then the total cost is equal to the sitting fee plus cost of enlargements.

Cost of enlargements = number of enlargements ordered times cost per 1 enlargement.

Cost of enlargements = n × 10

Total cost = 50 + 10n

180 = 50 + 10n

180 - 50 = 50 - 50 + 10n

130 = 10n

130/10 = 10n/10

13 = n

The customer ordered 13 enlargements.