Impedance load matching
\$Z_L=10+\frac{1}{j\omega C}\$ turns out 10+j20, well it can't. \$\frac{1}{j\omega C} = \frac{-j}{\omega C}\$ , so it has to be negative. On the source side the conjugate complex would give a positive imaginary number, so an inductor.

$$Z_L=R_L+\frac{1}{j\omega C_L}=R_L-\frac{j}{\omega C_L}$$
$$Z_L={Z_S}^*$$
$$Z_S=R_L-\frac{1}{j\omega C_L}=R_L+\frac{j}{\omega C_L}$$
$$Z_S=R_S+j\omega L_S$$
$$R_S=R_L , \ \omega L_S=\frac{1}{\omega C_L}$$