3甲+7乙+1丙=24 (1)
4甲+10乙+1丙=33 (2)
(2)-(1)得:1甲+3乙=9 两边同时×2得 2甲+6乙=18 (3)
(1)-(3)得:
1甲+1乙+1丙=6
则此人购买甲乙丙各一件要6元