Answer:
540°
Step-by-step explanation:
An equilateral triangle has 3 interior angles of 60°
A square has 4 interior angles of 90°.
When the images are joined, two vertices of each figures are joined together, such that these angles will have now a measure of:
60° + 90° = 150°
Then this figure has:
one angle of 60°
two angles of 150°
and two angles of 90°
(the image below illustrates this situation)
The sum of the interior angles is:
S = 60° + 2*150° + 2*90° = 540°
