Three angles out of four, obtained at the intersection of two straight lines, add up to 240 *. What is the fourth angle?

Let’s denote by x the value of one of these three angles, which add up to two hundred and forty degrees.

Then one of the other two corners will be adjacent to the first corner, and with the third corner the first corner will form vertical angles.

Therefore, the value of the 2nd angle should be 180 ° – x, and the 3rd angle – x and we can draw up the following equation:

x + 180 – x + x = 240,

solving which, we get:

x + 180 = 240;

x = 240 – 180 = 60 °.

Therefore, the 4th angle equal to the 2nd angle is 180 – 60 = 60 °.

Answer: 60 °.