The cost of 5 boxes of small paper clips and 2 boxes of large paper clips is $49.30. 7 boxes of small clips and 4 boxes of large ones cost $79.10. Find the cost of a box of each size of paper clips.

5x + 2y = 49.30

7x + 4y = 79.10

5x + 2y = 49.3

2y = 49.3 - 5x

y = 24.65 - 2.5x

7x + 4 (24.65 - 2.5x) = 79.1

7x + 98.6 - 10x = 79.1

-3x = - 19.5

x = 6.5

5 (6.5) + 2y = 49.3

32.5 + 2y = 49.3

2y = 16.8

y = 8.4

big box = $8.40

small box = $6.50