1又13/15*7+1又8/15*28
=28/15x7+23/15x28
=28/15x7+28/15x23
=28/15x(7+23)
=28/15x23
=56
80/4又1/2*0.125/（1-7/9）
=(80x0.125)÷(9/2x2/9)
=10 ÷1
=10
7又1/2*3.8+1/5/2/15
=15/2x3.8+0.2x15/2
=15/2x(3.8+0.2)
=15/2x4
=30
47.5*1/5+28*0.2+24.5/5
=47.5x0.2+28x0.2+24.5x0.2
=(47.5+28+24.5)x0.2
=100x0.2
=20
如果本题有什么不明白可以追问,