Bài `3`
`y xx 2 1/3=3/4`
`=> y xx (2xx3+1)/3 =3/4`
`=> y xx 7/3 =3/4`
`=> y= 3/4 : 7/3`
`=> y= 3/4 xx 3/7`
`=> y= 9/28`
bài `4`
`A= ( 1/4 + 1/2 : 2 1/3) xx ( 3 4/5 + 1/5)`
`A= ( 1/4 + 1/2 : (2xx3+1)/3 ) xx ( (3xx5+4)/5 + 1/5)`
`A= ( 1/4 + 1/2 : 7/3) xx ( 19/5 + 1/5)`
`A= ( 1/4 + 1/2 xx 3/7) xx 20/5`
`A= ( 1/4 + 3/14) xx 4`
`A= 13/28 xx 4`
`A= 52/28`
`A= 13/7`