I am thinking of a number . I multiply it by 3 and add 139 . I get the same answer if I multiply by 10 and subtract 8 . What is my number ?

Question

I am thinking of a number . I multiply it by 3 and add 139 . I get the same answer if I multiply by 10 and subtract 8 . What is my number ?

Answer 1

You first need to translate these into equations:

Multiply it by 3 and add 139 ----> 3x + 139

Multiply by 10 and subtract 8 -----> 10x -8

 

It says you get the same answer if you perform these two different problems, so you set the two equations equal to each other and solve for x:

3x +139 = 10x - 8

139 = 7x - 8 <---- Subtract 3x from both sides

147 = 7x <---- Add 8 to both sides

21 = x <---- Divide both sides by 7

 

So your number is 21.