Đáp án+Giải thích các bước giải:
`15.`
`(3.5.11.13)/(33.35.37)`
`=(3.5.11.13)/(3.11.5.7.37)`
`= 13/(7.37)`
`= 13/259`
`16.`
`(23.5-23)/(4-27)`
`= (23.(5-1))/(-23)`
`= 92/-23 = -4`
`17.`
`(18.13-13.3)/(15.40-80)`
`= (13.(3 - 18))/(15.40-2.40)`
`= (13.(-15))/(40.13)`
`= -15/40 = -3/8`
`18.`
`-22/15 -1 3/8 + 7/15 -2 5 /8`
`=-22/15 -11/8 + 7/15 - 21/8`
`= -11/120 + 7/15 - 21/8`
`= 3/8 - 21/8`
`=-9/4`
`19.`
`11/16 - 25 % . 3/4 + 75% : 4/5`
`= 11/16 - 1/4 . 3/4 + 3/4 : 4/5`
`= 11/16 - 3/16 + 15/16`
`= 1/2 + 15/16`
`= 23/16`
`20.`
`-8/19 - ( 3/4 + 11/19 )`
`= -8/19 - 101/76`
`= -7/4`