This is the 12839th most frequent Spanish word.
pagarle
"To pay him/her/you (formal)."
In this sentence, 'pagarle' signifies the action of paying a singular individual (him/her).
Debo pagarle el dinero que me prestó.
I must pay him the money he lent me.
Here, 'pagarle' is used to refer to compensating a person (the waitress).
Voy a pagarle a la mesera por el servicio.
I am going to pay the waitress for the service.
'Pagarle' in this context indicates settling the payment owed to the mechanic.