`A = (63/(9.18) + 21/(14.17)) : (14/(9.13) + 14/(14.18) + 14/(3.17))`
` = ((9.7)/(9.18) + (7.3)/(7.2.17) ) : (14/117 + 1/18 + 14/51)`
` = (7/18 + 3/(2.17)) : (476/3978 + 221/3978 + 1092/3978)`
`= (7/18 + 3/34) : 1789/3978`
` = (119/306 + 27/306) . 3978/1789`
` = 73/153 . 3978/1789`
` = (73 . 3978)/(153.1789)`
`= (73 . 153 . 26)/(153 . 1789)`
` = (73 . 26)/1789`
` = 1898/1789`
Vậy `A = 1898/1789`