How would I write the equation?

Question

They purchase a combination of 80 large binders and small binders. The large binders cost $8.49 each and the small binders cost $5.99 each. If the cost of the binders was $544.20. How many of each size were purchase

Answer 1

s represents the number of small binders

80 - s represents the number of large binders

5.99s + 8.49(80 - s) = 544.20

 

Can you solve for s and answer?