几个简算题，大家帮帮忙啊

七又九分之一乘以（八分之七-0.125）
=64/9*(7/8-1/8)
=64/9*3/4
=16/3
后两题用裂项
(2)3/4+3/28+3/70+3/130
=3/1*4+3/4*7+3/7*10+3/10*13
=(1/1*4+1/4*7+1/7*10+1/10*13)*1/3
=(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13)*1/3
=12/13*1/3
=12/39
(3)4/4*5+4/5*6+4/6*7+4/7*8+4/8*9+4/9*10
=(1/4*5+1/5*6+1/6*7+...+1/9*10)*1/4
=(1/4-1/5+1/5-1/6+1/6-1/7+...+1/9-1/10)*1/4
=3/20*1/4
=3/80

1.7(1/9)*(7/8-0.125)
=(64/9)*(7/8-1/8)
=(64/9)*(6/8)
=16/3.

2.3/4+3/28+3/70+3/130
=21/28+3/28+3/70+3/130
=24/28+3/70+3/130
=6/7+3/70+3/130
=60/70+3/70+3/130
=63/70+3/130
=9/10+3/130
=117/130+3/130
=120/130
=12/13.

3.4/4*5+4/5*6+4/6*7+4/7*8+4/8*9+4/9*10
=4(1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10)
=4(1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
=4(1/4-1/10)
=4(3/20)
=3/5.