Question

20 multiplied by a number, decreased by 15 equals 25. How do you find the number?

Answer 1

See full explanation for finding the number below

Explanation:

To solve this world problem we will convert it to a math problem to solve one phrase at a time.

"by a number" - let's call the number `n`.

"20 multiplied by a number" or by `n` can be written as:

`20 xx n` or `20 * n` or what we will use `20n`

"decreased by" means to subtract what follows which in this case is "15" so we can expand what we are writing to:

`20n - 15`

"equals 25" is the same as `= 25` so we can add this to our expression to get our equation:

`20n - 15 = 25`

We can now solve:

`20n - 15 + color(red)(15) = 25 + color(red)(15)`

`20n - 0 = 40`

`20n = 40`

`20n/color(red)(20) = 40/color(red)(20)`

`color(red)(cancel(color(black)(20)))n/cancel(color(red)(20)) = 2`

`n = 2`