The sum of the three angles formed by two intersecting straight lines is 243 °. Find all the angles.

Two of the three angles formed by two intersecting straight lines are vertical angles and are therefore equal to each other.

Let’s denote the value of these vertical angles through x.

The third angle formed by these two intersecting straight lines is adjacent for each of the two vertical angles and according to the properties of the adjacent angles, the third angle is 180 – x.

According to the condition of the problem, the sum of these three angles is 243 °, therefore, we can make the following equation:

x + 180 – x + x = 243.

Solving this equation, we get:

180 + x = 243;

x = 243 – 180;

x = 63 °.

We find the value of the third angle:

180 – x = 180 – 63 = 117 °.

Answer: These intersecting straight lines form angles of 63 ° and 117 °.