A series LCR circuit is connected to an AC source of 220V , 50Hz ....

Power factor in LCR circuit is given by,

$cosϕ = \dfrac{R}{Z}$, where, $Z$ is the total impedance of the circuit.

So, $cosϕ = \dfrac{R}{\sqrt{{R}^{2} + {\left({X}_{C} - {X}_{L}\right)}^{2}}}$

Putting the values, we have

$⇒ cosϕ = \dfrac{80}{\sqrt{( 80{)}^{2} + ( 60{)}^{2}}}$

$⇒ cosϕ = \dfrac{80}{100} ⇒ \dfrac{8}{10}$

Thus, the value of $x = 8$.