For x to be a solution, there must be the quantity x in the equation.
All the equations that contain x are :
+) 24 - 2x = 13
+) 4 + 5x = 18
+) 2x - 3 = 15
+) 3x + 2 = 25
We will solve for the value of x for each of the equation :
+) 24 - 2x = 13
-> 2x = 24 - 13 = 11
-> x = 11/2 = 5.5
+) 4 + 5x = 18
-> 5x = 18 - 4 = 14
-> x = 14/5 = 2.8
+) 2x - 3 = 15
-> 2x = 15 + 3 = 18
-> x = 18/2 = 9
+) 3x + 2 = 25
-> 3x = 25 - 2 = 23
-> x = 23/3.
We can see, only the equation 2x-3 = 15 has x=9 as a solution.