Garden sides:
7x+15
4x-1
Perimeter , sum of all sides:
P = 2 (7x+15) + 2 (4x-1) = 14x+30 +8x-2 = 22x +28
She will need 22x+28 feet of material
Current material = 13x+19
Material offered by the neighbor: 6x+5
Add both :
13x+19+6x+5 = 19x+24
She has no enough material.
22x+28 - (19x+24) = 22x-19x + 28 -24 = 3x + 4
She will need 3x+4 ft more material