[Tennessee Nana]

Watch $144
Chain $54
Locket $18

[SeekAndFind]

Very good. Simulataneous equations does the trick:

W = price of watch
C = price of chain
L = price of locket

W + C + L = 216 — equation 1
W - 3c + L = 0 — equation 2
0.5W + C + L = 0 — equation 3

A 10th grader in a good school in the USA could solve this.

[SeekAndFind]

TYPO 0.5W -0.5W + C + L = 0 — equation 3
Missing the negative sign will kill you.

[ninergold3]

Show Off. LOL ;}