Given that A, B, and C are collinear and B lies between A and C, then:
AB + BC = AC
Replacing with data:
(2x + 2) + (3x + 6) = 48
(2x + 3x) + (2 + 6) = 48
5x + 8 = 48
5x = 48 - 8
5x = 40
x = 40/5
x = 8
Then,
BC = 3x + 6
BC = 3(8) + 6
BC = 24 + 6
BC = 30