if 5/n-1/2=3/36, what is the value of n?
posible answers: -2, 2, 9, 2/7
we can start by reducing the fractions to get
$\displaystyle \frac{5}{n}-\frac{1}{2}=\frac{1}{12}$
The LCD of the equation is 12n so we multiply the whole equation by 12n to get
$\displaystyle \frac{60n}{n}-\frac{12n}{2}=\frac{12n}{12} \iff 60-6n=n$
$\displaystyle 60=7n \iff n=\frac{60}{7}$
This is not one of your choices but It is correct lets check and make sure.
So I will plug this into the original equation to get
$\displaystyle \frac{5}{\frac{60}{7}}-\frac{1}{2}\overbrace{=}^{?}\frac{1}{12}$
$\displaystyle \frac{35}{60}-\frac{1}{2}\overbrace{=}^{?}=\frac{1}{12}$
Getting a commond denominator I get
$\displaystyle \frac{35}{60}-\frac{30}{60}\overbrace{=}^{?}=\frac{1}{12}$
$\displaystyle \frac{5}{60}\overbrace{=}^{?}=\frac{1}{12}$
$\displaystyle \frac{1}{12}=\frac{1}{12}$
So the solution checks.
I hope this helps.