Answer:
k = 143
Step-by-step explanation:
Use the point-slope formula for the equation of a straight line:
y-h = m(x-k), where (h,k) is one of the given points and m is the given slope (-15). Here I'll use the point (-4,k).
y-k = -15(x-[-4]), or y - k = -15(x+4). Now use info from the other point: x=6 and y = -7:
-7 - k = -15(6+4). Here we have enough info to be able to find k.
Solving for -k, we get -k = 7 - 90 - 60, or -k = -143. Then k = 143.
