① 7/25×101-7/25
=7/25×(101-1)
=7/25×100
=28
②（5/6+7/8-5/12）÷1/2
=(5/6+7/8-5/12)×2
=5/6×2+7/8×2-5/12×2
=5/3-5/6+7/4
=5/6+7/4
=10/12+21/12
=31/12
③ 75%×3/7+1/7×3/4+3/7×0.75
=0.75×（3/7+1/7+3/7）
=0.75×1
=0.75弄错了！②（5/6+7/8-5/12）÷1/24=