A number minus 3 times 3 is that number

Question

x-3•3=x

Answer 1

Careful now, does the multiply go first or the subtraction?

 

As written: x - 3*3 = x

                 x - 9 = x <--- 3 times 3 is 9

                 -9 = 0  <--- subtracts x from both sides

  Since it is a false statement, there is no solution to this equation.

 

 

BUT...

 

 3 times the DIFFERENCE of some number and 3 is that number

 

 3(x-3) = x

 

 3x - 9 = x  <--- distributive property

 

 2x - 9 = 0  <--- subtracts x from both sides

 

 2x = 9  <--- adds 9 to both sides

 

 x = 9/2  <--- divides both sides by 2

 

CHECK:

 3(x-3) = 3( 9/2 - 3) = 3 ( 9/2 - 6/2) = 3(3/2) = 9/2 = x

 

So in this case the number is 9/2 or 4 and 1/2 = 4.5