Answer:
x = 20
Step-by-step explanation:
from how the sides are marked it is an equilateral triangle, to see it does not seem. assuming that it is equilateral it has 3 angles of 60 ° for which 4x - 20 = 60
4x - 20 = 60
4x = 80
x = 80 : 4
x = 20
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4 * 20 - 20 = 60°
