Question

what is the mechanical advantage of a pulley block

Answer 1

A block and tackle is characterized by the use of a single continuous rope to transmit a tension force around one or more pulleys to lift or move a load. Its mechanical advantage.

Answer 2

The mechanical advantage of a single pulley is 1. The easiest way to find Mechanical advantage is , MA= n, where 'n' stands for number of pulleys attached together.
I guess the diagram will make it more clear.