1. y = ax.
12 = -2a. a = -6.
y = b/x.
2 = b/5. b = 10.
b - a = 16.
2. y = ax.
-6 = 2a. a = -3.
y = b/x
-6 = b/2. b = -12.
ab = 36.
3. xy = 14.
y = 14/x.
4. xy = -15. y = -15/x
k = -15/(5/2) = -30/5 = -6