Cancel out $2m+3n$ in both numerator and denominator.
$$\frac{1}{2m-3n}-\frac{2}{2m-3n}$$
Since $\frac{1}{2m-3n}$ and $\frac{2}{2m-3n}$ have the same denominator, subtract them by subtracting their numerators. Subtract $2$ from $1$ to get $-1$.
Cancel out $2m+3n$ in both numerator and denominator.
$$\frac{1}{2m-3n}-\frac{2}{2m-3n}$$
Since $\frac{1}{2m-3n}$ and $\frac{2}{2m-3n}$ have the same denominator, subtract them by subtracting their numerators. Subtract $2$ from $1$ to get $-1$.
