Answer:
15(1/3b+3)≤6(b+9)
3b+3×15(1/3b+3)≤3b+3×6(b+9)
15≤3b+18(b+9)
15≤21b+162
162-15≤216
147≤216
147/21≤b
7≤b
b≤7
