Remember the acronym "Oil Rig". Oxidation is loss, Reduction is gain of electrons. Calcium is losing electrons so it's an oxidation reaction.
Ms ( mass of solute): 33,6g
mss (mass of solution): 33,6+192g = 225,6g
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C = ms/mss × 100%
C = 33.6/225.6 × 100%
C = 14,89% ≈ 14,9%
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