sensor - How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

I cannot understand how 3-wire measurement will improve the resistance measurement.

They say that IF lead resistance \$ R_L \$ is the same, it will compensate. How can this happen?

If bridge is balanced (without \$ R_L \$): \$ \frac {R_1}{R_2} = \frac {R_g}{R_3} \$

If \$ R_L \$ is added: \$ \frac {R1}{R2}= \frac {R_g+R_L}{R_3+R_L} \$

\$ \frac {R_g}{R_3} \$ is not same as \$ \frac {R_g+R_L}{R_3+R_L}\$; is this true only if \$ R_G=R_3 \$ in the beginning? So this means that \$R_L\$ does not get compensated?