Answer:
The answer would be B.
Explanation:
Just substitute x for 5.
For example, A is 2+x=3.
Just put 5 instead of x.
It would be 2+5=3.
But that isn't the answer because 2+5 is 7, not 3.
For B, sub the x for 5 just like we did for A.
It would usually be 3x=15
But sub the x with 5.
It would turn into 3x5=15
And that is right, because if you multiple 5 three times, it would be 15.
I hope this helps, I did my best. Have a great day!