How do I find C & L from XC and XL?
Where


\$f\$ is frequency in hertz
\$C\$ is capacitance in farads
\$X_C \$ is capacitive reactance in ohms 
\$L\$ is inductance in henrys, and
\$X_L\$ is inductive reactance in ohms,


and you start with:

$$ X_L = 2 \ \pi \ f\ L, $$

then divide both sides of the equation by \$2\pi\ f\$ in order to isolate the \$ L\$, you'll get: 

$$ \frac {X_L}{2 \ \pi \ f}= \frac{ \require{cancel} \cancel { 2 \ \pi \ f}\ L}{ \require{cancel} \cancel { 2 \ \pi \ f}}\text{ .} $$

Move the \$L\$ over to the left hand side and, like magic, Voila!
$$ L= \frac{X_L}{2 \ \pi \ f}\ $$

Rearranging to get the capacitance, if you start with:

$$Xc = \frac{1}{2 \ \pi \ f\ C}  $$

and multiply both sides of the equation by C, in order to put C in a less cumbersome place to work with, you'll get:

$$C\ X_C = \frac{1\require{cancel} \cancel {C}}{2 \ \pi \ f\require{cancel} \cancel {C}} $$

Finally, in order to isolate C and put the reactive term in its place, divide through by\$ X_C\$ and you'll get: 

$$ \frac{C \require{cancel} \cancel {X_C}}{\require{cancel} \cancel {X_C}} = \frac{1}{2\pi\ f\ X_C}{ \text{ , }} $$ and after you clean it all up you'll have:

$$ C  = \frac{1}{2\pi\ f\ X_C}$$