(1/2 +1/6 +3/4)×252=1/2×252+1/6×252+3/4×252=126+42+189=357
(1/2 + 1/6 + 3/4)x252=(1/2)x252+(1/6)x252+(3/4)x252=126+42+3x63=125+42+189=356