Answer:
The other coordinate is (-6,19)
Step-by-step explanation:

(4,-7)
(x,y)
[(4+x)/2 , (-7+y)/2] = (-1,6)
(4 + x)/2 = -1
4 + x = -2
× = -6
(-7 + y)/2 = 6
-7 + y = 12
y = 19
(Correct me if i am wrong)
Answer:
25, i had the same question
What they said ^ I was just about to answer, but there’s popped up first lol
Y-4X =3 ; 2x-3y=21
Y= 3+ 4x
2x -3( 3+4x)= 21
2x- 9- 12x= 21
-10x -9= 21
-10x -9+9= 21+9
-10x = 30
X= 30/-10= -3
Y= 3+4x = 3+ 4* (-3)= 3-12= -9