【1又1/24-（3/8+1/6-3/4）×24】×2/5 =（1又1/24-3/8x24-1/6x24+3/4x24）x2/5=(1又1/24-9-4+18)x2/5=(25/24+5)x2/5=25/24x2/5+5x2/5=5/12+2=2又5/12
