Substitute x=15 in the first expression 2(x+3)=40.
36 is not equals to 40. Thus, the above expression is wrong.
Substitute x=15 in the second expression. 2(x-5)=30
The above expression is also not true since 20 is not equals to 30.
Substitute x=15 in the third expression. 2(x+5)=40
The above expression is true. Thus, the value x=15 is true for the expression 2(x+5)=40.