I can't answer your question without a picture... Sorry.
Here are a few reasons:
The triangles have the same three sides
The triangles have the same three angles
The triangles could perfect overlap one another
They have corresponding angles.
Not sure if this helped but I hope so!
The value of y-x is (-3)
<u>Solution:</u>
Given: The value of x-y=3
To find: The value of y-x

Let's multiply the equation (1) by (- 1) on both sides,


On multiplying the sign,

The above equation can also be written as,

<u>Multiplication of signs:</u>




In simpler terms, when we multiply two integers with the same signs, the result is always positive and when we multiply two integers with different signs, the result is always negative.
B. is the answer if you look closely