Answer:

Step-by-step explanation:
distance between two points:

we have:
(-4, -6), (3, -7)




so we have:

Step-by-step explanation:
When x=-3
7-2(-3)=7-(-6)
=7+6
=13
The mistake is that they subtracted 21 instead of adding it. you would have had to added 21 to the left side to cancel it out and added 21 to the right side to get p= 55