Answer (Note: the bold are answers):
First question answer:
Point = (3,1)
Slope = 3
y = 3x + b
(1) = 3(3) + b
1 = 9 + b
1 - 9 = b
-8 = b
y = 3x - 8
The second question answer:
y = mx + b
Get two points:
(3,-7) and (4,-11)
m = -11 - (-7) / 4 - 3
m = -11 + 7 / 1
m = -4 / 1
m = -4
b = + 3
y = -4x + 3