Find the measure of angle 3

There are 20 children in the cast of a class play and 8 of the children are boys of the boys 4 have a speaking part in the play and of the girls 8 do not have a speaking part in the play if a child from the cast of the place chosen at random what is the probability that the child has a speaking part

What is the value of x in the diagram below?

Multiply. write your answer in simplest form. 3/8 x 5/7