HELP ASAP!!! Reflect the triangle across the dashed line and enter the new coordinates. Enter the number that belongs in the green box. ALL ANSWERS PLEASE!!! WILL MARK BRAINLIEST!!!

Answer:
Step-by-step explanation:
The triangle is being reflected over the y-axis.
A(x, y) → (x, -y)
A(1, 4) → (1, -4)
A'(1, -4)
B(x, y) → (x, -y)
B(4, 3) → (4, -3)
B'(4, -3)
C(x, y) → (x, -y)
C(2, 1) → (2, -1)
C'(2, -1)
Hope this helps!