Kathy starts with a number. She adds 3 to her number then doubles the result. Finally she subtract 7. If she ended with 9 what number did she start with?

Mathematics · Middle School · Wed Jan 13 2021

Answered on

Let the number be x

Then, she adds 3. So,

x + 3

Then, number is doubled,

2(x+3)

2x + 6

Now, 7 is subtracted

2x + 6 - 7

2x - 1

Then, result is 9. So,

2x -1 = 9

2x = 9 + 1

2x = 10

x = 10/2

x = 5

 

Thus, she started with 5.