I am thinking of a number....

I multiply it by 6 and add 66. I get the same answer if I multiply by 10 and subtract 10.
What is my number? (Please show me your working out)

You need to make an equation.
10n-10=6n+66 float and ping n=any number
10n-6n=66+10
4n=76
n=76/4
n=19

To prove that the answer is right
6x19=114 114+66=180
10x19=190 190-10=180

10x-10=6x+66
4x-10=66
4x=76
x=19

6x+66= X
10x-10=X
6x+66=10x-10
6x+76=10x
76=4x
x=76/4