Let:
Ms. Barton = b
Mr. Weaver = b + 8
Mr. Fitzgerald = 2b - 15
Mr. Lloyd = 1/2b + 30
Find b:
176 = b + b + 8 + 2b - 15 + 1/2b + 30
176 = 9/2b + 23
153 = 9/2b
b=34
Plug in 9 to b:
Ms. Barton = 34 slices (4th place)
Mr. Weaver = 34 + 8 = 42 slices (3rd place)
Mr. Fitzgerald = 2(34) - 15 = 53 slices (1st place)
Mr. Lloyd = 1/2(34) + 30 = 47 slices (2nd place)