This question is just a question targeted towards puzzling the solver. It is infact a very easy problem. In the given question the information's provided should be very minutely watched. First information says that there is an unknown number. The problem revolves around this unknown number and various information's show that this number is always connected with the majority information's provided.
Let us assume the unknown number = x
Then
2x -4 = x - 10
2x - x = - 10 + 4
x = - 6
So the unknown number is -6.
The missing angle of the given triangle is 59°.
What is vertically opposite angles?
Angles that are vertically opposed to one another are always equal to one another. A vertical angle and the angle to which it is next are also supplementary angles; that is, they sum up to 180 degrees. As an illustration, if two lines connect to form an angle, say X=45°, then the angle's opposite angle is also 45°.
Here consider angle with 31° and 49° triangle is 1. We know that sum of all angles in triangle is add upto 180°. Then,
⇒ 49°+31°+x = 180°
⇒ 80° + x= 180°
⇒x= 180°-80°=100°
Then unknown angle in triangle 1 ia 100°.
Now according to the vertically opposite angle theorem , opposite angles are equal to each other. Then ,
In triangle 2 angle is 100° and 21°. Then missing angle is,
⇒ 100°+21°+missing angle =180°
⇒Missing angle = 180°-100°-21°
⇒Missing angle = 59°
Therefore the answer is 59°.
To learn more about Vertical angle ,
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Answer: C. Along the rows and columns .
Step-by-step explanation: