Solve for L QL-3rL=N

$Q L - 3 r L = N$

Factor $L$ out of $Q L - 3 r L$ .

Factor $L$ out of $Q L$ .

$L Q - 3 r L = N$

Factor $L$ out of $- 3 r L$ .

$L Q + L (- 3 r) = N$

Factor $L$ out of $L Q + L (- 3 r)$ .

$L (Q - 3 r) = N$

Divide each term in $L (Q - 3 r) = N$ by $Q - 3 r$ and simplify.

Divide each term in $L (Q - 3 r) = N$ by $Q - 3 r$ .

$\frac{L (Q - 3 r)}{Q - 3 r} = \frac{N}{Q - 3 r}$

Simplify the left side.

Cancel the common factor of $Q - 3 r$ .

Cancel the common factor.

$\frac{L (Q - 3 r)}{Q - 3 r} = \frac{N}{Q - 3 r}$

Divide $L$ by $1$ .

$L = \frac{N}{Q - 3 r}$