Kristen spent $131 on shirts. Fancy shirts cost $28 and plain shirts cost $15. If she bought a total of 7 then how many of each kind did she buy?

1 x + 1 y = 7 ... 1

Total value

15 x + 28 y = 131 ... 2

Eliminate y

multiply (1) by - 28

Multiply (2) by 1

-28 x - 28 y = - 196

15 x + 28 y = 131

Add the two equations

-13 x = - 65

/ - 13

x = 5

plug value of x in (1)

1 x + 1 y = 7

5 + y = 7

y = 7 - 5

y = 2

y = 2

x = 5 plain shirts

y = 2 fancy shirts