Answer:
Just some background:
Congruent means that a triangle has the same angle measures and side lengths of another triangle.
SAS congruence theorem: If two sides and the angle between these two sides are congruent to the corresponding sides and angle of another triangle, then the two triangles are congruent. Congruent triangles: When two triangles have the same shape and size, they are congruent.
Let's look at A first.
The triangle on left, we know 40 and 30 degree angles. So 3 all angles together = 180, so the 3rd angle = 180-30-40 = 110.
Now look at the triangle on the right. The angle shown is 110! This angle is between the sides marked with || and ||| marks, indicating that those two sides are the same length between both triangles.
Therefore both triangles are the same by Side-Angle-Side or SAS.
Now look at B.
It's a right triangle. We are missing 1 side of each triangle.
Let's solve for the missing "leg" of the triangle on the right. The pythagorean theorem says that a^2 + b^2 = c^2 where a and b are the 'legs' or sides of the triangle and c is the hypotenuse (always the longest length opposite the right angle).
so 2^2 + b^2 = 4^2
4 + b^2 = 16
b^2 = 16-4
b^2 = 12
That missing side is the
.
This does NOT match the triangle on the left.
Theses two triangles are NOT congruent.