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

2 Answers
May 8, 2018

13 years old

Explanation:

Pat's age today is a variable since we don't know its value. Let's say that's xx.
Pat's age 5 years ago would be x-5x5.

Add those together and you have 21, so...
xx added to x-5x5 is 21.21.

Mathematical form: x+(x-5)=21x+(x5)=21
Let's simplify!

x+x-5=21x+x5=21
2x-5=212x5=21
2x=262x=26
x=13x=13


Checking your work:
(13)+(13)-5\stackrel(?)(=)21(13)+(13)5?=21
26-5\stackrel(?)(=)21265?=21
21=21\sqrt21=21

May 8, 2018

Pat is 13 years old

Explanation:

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

P+(P-5)=21P+(P5)=21

P+P-5=21P+P5=21

2P-5=212P5=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)