Question

15 times a certain number plus 5 times the same number is 80 what is the number​

Answer 1

Let the number be x

ATQ

`\\ \sf\longmapsto 15x+5x=80`

`\\ \sf\longmapsto (15+5)x=80`

`\\ \sf\longmapsto 20x=80`

`\\ \sf\longmapsto x=(80)/(20)`

`\\ \sf\longmapsto x=4`

Answer 2

x = 4

Every step shown. Once you become used to doing this you will almost be able to do the basic one's in your head without writing much down.

Explanation:

Let the unknown value be

x

Converting the words into numbers:

First part: "15 times a certain number" → 15 x

Second part: "plus 5 times the same number" → 15 x + 5 x

The last part: " is 80" -> 15x + 5 x = 80

We are counting x ' s . 15 of them plus another 5 of them gives a total of 20.

So 15 x + 5 x = 20 x = 80

Divide both sides by 20

20 x ÷ 20 = 80÷ 20

20/20x=80/20

x=4