Đáp án `+` Giải thích các bước giải:

`4)` `\text{17 . 35 + 17 . 65 - 50}`

`\text{= 17(35 + 65) - 50}`

`\text{= 17 . 100 - 50}`

`\text{= 1700 - 50}`

`\text{= 1650}`

`5)` `\text{21 . 78 + 21 . 22 - 50}`

`\text{= 21(78 + 22) - 50}`

`\text{= 21 . 100 - 50}`

`\text{= 2100 - 50}`

`\text{= 2050}`

`6)` `\text{17 . 85 + 15 . 17 - 120}`

`\text{= 17(85 + 15) - 120}`

`\text{= 17 . 100 - 120}`

`\text{= 1700 - 120}`

`\text{= 1580}`

`7)` `\text{13 . 75 + 13 . 25 - 140}`

`\text{= 13(75 + 25) - 140}`

`\text{= 13 . 100 - 140}`

`\text{= 1300 - 140}`

`\text{= 1160}`

`8)` `\text{11 . 49 + 51 . 11 - 100}`

`\text{= 11(49 + 51) - 100}`

`\text{= 11 . 100 - 100}`

`\text{= 1100 - 100}`

`\text{= 1000}`

`9)` `\text{85 . 75 + 25 . 85 - 500}`

`\text{= 85(75 + 25) - 500}`

`\text{= 85 . 100 - 500}`

`\text{= 8000}`

                                                   `color{#CC33FF}{K}color{#CC33CC}{a}color{#CC3399}{m}color{#CC3366}{a}color{#993366}{d}color{#993399}{o}` `color{#9933CC}{N}color{#9933FF}{e}color{#6633FF}{z}color{#6633CC}{u}color{#663399}{k}color{#663366}{o}` `color{#333366}{c}color{#333399}{u}color{#3333CC}{t}color{#3333FF}{e}`