what is the rule?
x 5 7 9 11
y 1 1.6 1.8 2.2
Hmmm. The successive differences are
0.6 0.2 0.4
so it's not linear. The simplest curve to fit 4 points is a cubic. That means that one rule to fit the table is
1/40 (5x^3 - 107x^2 + 751x - 1665)
Somehow I don't think that's what was intended.
Now, if the second value is supposed to be 1.4, then we have a uniform change of 0.4 in y when x changes by 2. Thus, the slope of the line is
0.4/2 = 0.2 and the rule is thus
y = 0.2x