Bài 1 (1,0 điểm). Thực hiện phép tính: a) $\frac{-20}{23}$ + $\frac{2}{3}$ - $\frac{3}{23}$ + $\frac{2}{5}$ +$\frac{7}{5}$  b) $1\frac{13}{15}$ . $(0,5)^{2}$ .3 + ($\frac{8}{15}$ -$1\frac{19}{60}$): $1\frac{23}{24}$ 

Đáp án + Giải thích các bước giải:

`a)` `-20/23` `+` `2/3` `-` `3/23` `+` `2/5` `+` `7/5`

`=` `(` `-20/23` `-` `3/23` `)` `+` `(` `2/5` `+` `7/5` `)` `+` `2/3`

`=` `(` `-1` `)` `+` `9/5` `+` `2/3`

`=` $\dfrac{-15}{15}$ `+` `27/15` `+` `10/15`

`=` `22/15`

Đề trong hình:

`-20/23` `+` `2/3` `-` `3/23` `+` `2/5` `+` `7/15`

`=` `(` `-20/23` `-` `3/23` `)` `+` `2/3` `+` `(` `2/5` `+` `7/15` `)`

`=` `(` `-1` `)` `+` `2/3` `+` `(` `6/15` `+` `7/15` `)`

`=` `(` `-1` `)` `+` `2/3` `+` `13/15`

`=` `-15/15` `+` `10/15` `+` `13/15`

`=` `8/15`

`b)` `1``13/15` `.` `(` `0,5` `)`$^2$ `.` `3` `+` `(` `8/15` `-` `1``19/60` `)` `:` `1``23/24`

`=` `28/15` `.` `0,25` `.` `3` `+` `(` `8/15` `-` `79/60` `)` `:` `47/24`

`=` `7/15` `.` `3` `+` `(` `32/60` `-` `79/60` `)` `.` `24/47`

`=` `7/5` `-` `47/60` `.` `24/47`

`=` `7/5` `-` `2/5`

`=` `1`

   `- - -~kid20~- - -`