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.