a) `(1/5x-4/5)((2x-1)/3-2/6)=0`
`[(1/5 x-4/5=0),(2/3 x -1/3 -1/3=0):}`
`[(x=4),(x=1):}`
.
c) `50% x+2/3 x=x-5`
`1/2 x+2/3 x= x-5`
`(1/2+2/3-1)x=-5`
`1/6 x=-5`
`x=-30`
.
`A=3/(3.5)+3/(5.7)+....+3/(97.99)`
`=> 2/3 A = 2/(3.5)+2/(5.7)+....+2/(97.99)`
`=1/3-1/5+1/5-1/7+...+1/97-1/99`
`=1/3-1/99`
`=32/99`
`=> A=16/33`
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