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A number decreased by 5 and then doubled is equal to the same number increased by 25. What is the number?

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2 Answers

First you identify your variable, for our sake lets use x:

x= number in question

Next you write the equation given in the question:

2(x-5)= x+25

Next you use the distributive property and multiply 2 by both x and negative 5 to get:


Now you want to get all of the x's to one side so you subtract the x on the right, fro the one on the left giving you:


Then you simply add 10 to 25 giving you the answer of x=35.

n = unknown number

Decreased by 5 then  doubled means (n - 5)*2

The same number increased by 25 means n + 25

(n - 5)*2 = n + 25                Equation found from the story problem

2n - 10 = n + 25                   Distribute the 2

2n = n + 35                          Add 10 to each side

n = 35                                  Subtract n from each side