9/10 times a number plus 6 is 51

N = the number

9/10n + 6 = 51                                       Original Problem.
9/10n = 46                                            Subtract 6 from each side.
n = 51.11111111111111111111                  Multiply each side by (10/9)

n = 51.111111111111111111111

So,

Let's translate this into mathematical form.
"9/10 times a number"


"plus 6 is 51"
+ 6 = 51

So we have our equation:


Subtract 6 from both sides.


Multiply both sides by the reciprocal of 9/10 (10/9).


Multiply.


The number is 50.

Check.


Multiply.


Add.

This checks.

S = {50}

The correct answer is: 2