What values of x and y satisfy -13/3 x-2 y=7 and 3x+2/5 y=5 simultaneously?

Multpiply first equation by 3 and second by 5 to clear nasty faractions

-13x-6y=21
15x+2y=25

now see which ones we can clear
we can clear y
multiply second equation by 3 and add to the first equation

-13x-6y=21
45x+6y=75 +
32x+0y=96

32x=96
divide both sides by 32
x=3

sub back
15x+2y=25
15(3)+2y=25
45+2y=25
minus 45 from both sides
2y=-20
divide both sides by 2
y=-10

x=3
y=-10
(3,-10)

No solution : there is no number of boxes that she bought