The rate of change of the first is 3.
To find the linear function for the second, assume y=mx+c. Plug in some values:
(-7,-10): -10=-7m+c;
(-5,-6): -6=-5m+c;
Subtract the two equations: -10-(-6)=-7m-(-5m); -4=-2m, m=2.
Plug in m=2, y=2x+c; -6=-10+c so c=4 and y=2x+4.
Check for consistency: put x=-3: y=-6+4=-2; x=-1: y=2; x=1: y=6; x=3: y=10. All consistent. Rate of change is 2. The greater rate of change is y=3x-4.