` \text{a)}`
`0,39 : 0,91 = x : 16 1/3`
`x : 49/3 = 3/7`
`-> x = 7`
Vậy `x =7`
$\\$
`\text{b)}`
`6,88 . x = 12 : 27`
`-> 6,88 . x = 12/27`
`-> x = 25/387`
Vậy `x = 25/387`
$\\$
`\text{c)}`
`8 1/3 . 11 2/3 = 13 : (2x)`
`-> 25/3 . 35/3 = 13 : 2x`
`-> 875/9 = 13 : 2x`
`-> 13 : 2x = 875/9`
`-> 2x = 117/875`
`-> x = 117/1750`
Vậy `x = 117/1750`
$\\$
`\text{d)}`
`(x-1) . 24,5 = 5 : 8,75`
`-> (x-1) . 24,5 = 4/7`
`-> x-1 = 8/343`
`-> x = 351/343`
Vậy `x = 351/343`
