Triangle A suffered several transformations.
First transformation is a reflection over the y=-1 line.
Keep in mind that any reflection, over the y or x axis or any line in the coordinate system will prodice a "mirroed image", this means that the triangle will be congruent to the initial one by it will be inverted.
The line y=-1 is a line parallel to the x-axis, this means that the x coordinates of each point of triangle A will remain the same and only the y-coordinates will change.
To determine this change you have to measure the distance between each point and the reflection line, then multiply said distance by two and considering that the reflection will be from the first quadrant to the fourth quadrant, subtract the calculated distance to the y-coordinate.
For point (2,4) its distance to the line y=-1 is 5 units (pink doted line)
Multiply that distance by two to determine the distance to the reflected point:
5*2=10
And subtract it to the y-coordinate of the point to determine the reflected coordinates:
(2,4-10)→(2,-6)
For point (2,1) its distance to the line y=-1 is 2 units (green line)
Multiply it by two: 2*2=4
Subtract it from the y-coordinate of the point and determine the reflected coordinates:
(2,1-4)→(2,-3)
For point (4,1) the distance is 2 units (light blue line)
Multiply it by 2: 2*2=4
Subtract the distance from the y-coordinate to determine the reflected coordinates:
(4,1-4)→(4,-3)
The coordinates of the triangle after a reflection over the line y=-1 are: (2,-6), (2,-3) and (4,-3). If you draw it you'll see that the corresponding triangle is E
Second tranfosrmation: 180º rotation about point (5,1)
The triangle was rotated after the reflection over the y=-1 line. So the rotation was performed over triangle "E"