Answer: y = 50
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Explanation:
For any kite, the adjacent sides are congruent.
This leads to AB = BC and AD = DC
Using the SSS congruence rule, we can prove triangle ABD is congruent to triangle CBD.
From that we can say
Angle ABD = Angle CBD
as these angles correspond to one another.
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So this means angle ABD is y
Let E be the intersection point of the diagonals. Angle AEB is x = 90 as you found earlier. The diagonals of any kite are always perpendicular.
Focus on triangle AEB
The three angles of any triangle add to 180
A+E+B = 180
40+x+y = 180
40+90+y = 180
130+y = 180
y = 180-130
y = 50
