So,
Let's translate this into mathematical form.
"9/10 times a number"
[tex] \frac{9}{10} n[/tex]
"plus 6 is 51"
+ 6 = 51
So we have our equation:
[tex] \frac{9}{10} n + 6 = 51[/tex]
Subtract 6 from both sides.
[tex] \frac{9}{10} n = 45[/tex]
Multiply both sides by the reciprocal of 9/10 (10/9).
[tex]n = (45) \frac{10}{9} [/tex]
Multiply.
[tex] \frac{45}{1} * \frac{10}{9} --\ \textgreater \ \frac{5}{1} * \frac{10}{1} = 50[/tex]
The number is 50.
Check.
[tex] \frac{9}{10} * 50 + 6 = 51[/tex]
Multiply.
[tex]45 + 6 = 51[/tex]
Add.
[tex]51 = 51[/tex]
This checks.
S = {50}
