Question

How do you evaluate `8- 12\div 3+ 21\div 7`?

Answer 1

The answer is `7`.

Explanation:

We use BODMAS to help solve this. There are no Brackets and no Orders, so we go straight to Division and then Multiplication, before going on to Addition and Subtraction. The direction is left to right.

`8-12-:3+21-:7`

There are no Brackets and nor Orders, so we go directly to Division.

There are two divisions from left to right: `12-:3=4` and `21-:7=3`

Hence:

`8-4+3`

Next comes Addition and Subtraction from left to right:

`8-4=4` and `4+3=7`

Answer 2

`=7`

Explanation:

Count the number of terms and simplify each to get a single value. These are added and subtracted in the last step.

`" "color(red)(8)color(blue)(-12div3)color(green)(+21div7)" "larr` there are 3 terms
`color(white)(xxxx.x)darrcolor(white)(xxx)darr`
`=color(red)(8)" "color(blue)(-4)" "color(green)(+3)`

`=color(red)(8)" "color(green)(+3)" "color(blue)(-4)" "larr` write the additions at the front

`=11-4`

`=7`