A,(2.872+0.25+2.166:0.1)x0.005 B, 1/2+3/5+3/7+3/11 TRÊN 4/5+4/7+4/11 C, 2019/2020 x 1/2021 + 2019/2020 : 2021/2020 x 1/2020

`a) (2,872 + 0,25 + 2,166 : 0.1) xx 0,005`

`= (3,122 + 21,66) xx 0,005`

`= 24,782 xx 0,005`

`= 0,12391`

`b) 1/2 + (3/5 + 3/7 + 3/11)/(4/5 + 4/7 + 4/11)`

`= 1/2 + (3xx(1/5 + 1/7 + 1/11))/(4xx(1/5 + 1/7 + 1/11))`

`= 1/2 + 3/4`

`= 2/4 + 3/4`

`= 5/4`

`c) 2019/2020 xx 1/2021 + 2019/2020 : 2021/2020 xx 1/2020`

`= 2019/2020 xx 1/2021 + 2019/2020 xx 2020/2021 xx 1/2020`

`= 2019/2020 xx 1/2021 + 2019/2020 xx 1/2021`

`= 2019/2020 xx (1/2021 + 1/2021)`

`= 2019/2020 xx 2/2021`

`= 4038/4082420`

`= 2019/2041210`