For the equation 3x = 13.5,
I substituted 4.5 for x.

3x = 13.5
3(4.5) 13.5
13.5 = 13.5

Since substituting 4.5 for x into the original equation generates a true statement, I think that
x = 4.5 is a solution of
3x = 13.5.

For the equation
x + 9.4 = 13.9,
I substituted 4.5 for x.

x + 9.4 = 13.9
(4.5) + 9.4 13.9
13.9 = 13.9

Since substituting 4.5 for x into the original equation generates a true statement, I think that
x = 4.5 is a solution of
x + 9.4 = 13.9.

For the equation
x − 3.7 = 7.2,
I substituted 4.5 for x.

x − 3.7 = 7.2
(4.5) − 3.7 7.2
0.8 ≠ 7.2

Since substituting 4.5 for x into the original equation generates an untrue statement, I think that x = 4.5 is not a solution of
x − 3.7 = 7.2.