Some one help me on this algebra problem please? kind of confused?

Question

So here is the problem i need help on, could you explain it step by step since im new to this please? thanks

if points (3,-7) and (-2,k) are on a line with slope -4, what is the value of k?

Answer 1

Given points (3,-7), (-2,k) and slope m=-4

say (x1,y1)=(3,-7);(x2,y2)=(-2,k)

the slope equation m=y2-y1/x2-x1

-4=k-(-7)/-2-3

the  product  of  two  same  signs is positive

-4=k+7/-5

-5*-4=k+7

the product of two same signs is positive

20=k+7

subtract  from  7 each  side

20 - 7 = k + 7 - 7

13=k

k=13