Answer:
whichever is the same on the y cordanate but not the x cordanate (opsite side of 0)
Step-by-step explanation:
Change the negativity of the first number in the cords are pair then chose that answer that is there
-21 = 6t
3t - 7 = 5t
Subtract 3t from each side
3t-7-3t = 5t-3t
-7 = 2t
Multiply each side by 3 to get 6t
-7*3 = 2t*3
30