Question

Pat's age today, plus Pat's age 5 years ago, equals 21. What is Pat's age today?

Answer 1

13 years old

Explanation:

Pat's age today is a variable since we don't know its value. Let's say that's `x`.
Pat's age 5 years ago would be `x-5`.

Add those together and you have 21, so...
`x` added to `x-5` is `21.`

Mathematical form: `x+(x-5)=21`
Let's simplify!

`x+x-5=21`
`2x-5=21`
`2x=26`
`x=13`

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Checking your work:
`(13)+(13)-5\stackrel(?)(=)21`
`26-5\stackrel(?)(=)21`
`21=21\sqrt`

Answer 2

Pat is 13 years old

Explanation:

Let's write the sentence in mathematical terms, using `P` as "Pat's Age"

`P+(P-5)=21`

`P+P-5=21`

`2P-5=21`

`2Pcancel(-5)color(red)(cancel(+5))=21color(red)(+5)`

`2P=26`

`(cancel(2)P)/color(red)(cancel(2))=26/color(red)(2)`

`color(green)(P=13)`