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