Answer:
y = 40°
Step-by-step explanation:
The triangle in the picture is an isosceles triangle because of the markings on the side (they show that two sides are congruent).
An isosceles triangle not only have a pair of congruent sides, but also have a pair of congruent angles.
So,
5x = 40
Solve for x,
x = 40 ÷ 5
x = 8
5x = 40
5(8) = 40
40 = 40
Now we know the two angles. We then find the last angle containing y.
We know that the total angle measurement of the triangle is 180°.
Set up the equation,
40 + 40 + 2y + 20 = 180
Solve for y,
80 + 2y + 20 = 180
100 + 2y = 180
2y = 180 - 100
2y = 80
y = 80 ÷ 2
y = 40°
