Find the corners of a quadrilateral if three angles are equal to each other, and the fourth is less than one of them by 40

From the condition, we are given a quadrilateral, and it is also known that the three angles of the quadrilateral are equal to each other, and the fourth angle is less than one of them by 40 °.

Let’s remember what the sum of the angles of a quadrilateral is equal to. The angles of a quadrilateral add up to 360 °.

Let us denote the angle of the quadrangle using the variable x, then the fourth angle can be written as (x – 40).

Let’s compose and solve a linear equation with one variable:

x + x + x + x – 40 = 360;

4x – 40 = 360;

4x = 360 + 40;

4x = 400;

x = 400: 4;

x = 100.

Three angles of the triangle are equal to 100 °, and the fourth is 100 – 40 = 60 °.