There are 30 red marbles and 10 black marbles in urn #1. you have 20 red and 20 black marbles in urn #2. randomly you pull a marble from the random urn and find that it is red.
what is the probability that it was pulled from urn #1?

Step-by-step explanation:

we know that

An isosceles triangle has two equal sides and two equal angles

The two equal angles are the base angles and the third angle is the vertex angle

In this problem

The vertex angle of one of the isosceles triangle is equal to

The sum of the internal angles of the triangle is equal to

Let

x------> the measure of a base angle of one of the isosceles triangle

so

solve for x