-0.875-(-1又1\4)+3\4+1又7\8
=（1又7/8-7/8）-(1又1/4-3/4)
=1-1/2
=1/2
[2.4-（-2.7+3.5）-2.2]-（-6.7+5.4）
=2.4+2.7-3.5-2.2+6.7-5.4
=5.1-5.7+6.7-5.4
=6.1-5.4
=0.7