Question

a line passes through (1,1),(-2,4), and (6,n)
find value of n

Answer 1

since the slope is constant, you need

(n-4)/(6+2) = (4-1)/(-2-1)
Now you can find n.

Or, thinking about it another way,

y increased by 3 when x decreased by 3.

So, y will decrease by 8 if x increases by 8.

Answer 2

were did the postive 2 come from

Answer 3

6 - (-2)

C'mon, read your text.