Rangiora/Cashmere + Rangiora/Cashmere = A
A x Rolleston/New Brighton = B
B + Halswell/Queenspark = C
Shirley/Westmorland - Rangiora/Cashmere = D
D x Northwood/Huntsbury = E
E - Hillmorton/Southshore = F
F + Halswell/Queenspark = G
G x Rolleston/New Brighton = H
H + C = I
Wigram/The Palms - Southbridge/Lincoln = J
Rangiora/Pegasus x J = K
Burnside/Spreydon - Lincoln/Parklands = L
Styx Mill/Northlands x L = M
M + K = N
N - Rangiora/Cashmere = O
Eastgate/Lyttelton - The Palms/New Brighton = P
Russley/Mt Pleasant + Hei Hei/Avonhead = Q
Q x P = R
R + Redwood/Westlake = S
I + O + S = Your Answer
Checksum (E.g. 123 = 6) = 17
Note:
Logbook is a tight fit, replace cache EXACTLY as found.