I think this is suppose to be
x y
2 1400
4 1000
you see at 2 hours they have 1400 left and at 4 hours they have 1000 feet left.
first we need y intercept or b since we will put it in y=mx+b form
so at x= 0 whats y. Based on this every 2 hours you climb 400. so go back from x=2 to x=0 would make 1000 into 1800 feet left
so at x hours you have 1800 left
y - intercept is (0, 1800) or +1800
now we need slope
difference in y / difference in x
diff in y = 1400-1000 = 400
diff in x = 2 - 4 = -2
difference in y / difference in x = 400/-2 = -200 is the slope
y=mx+ b for
y=-200x+1800
