Answer:
A.The multiplication property of equality
Step-by-step explanation:
We are given that
If x=3 then 
We have to find that which property of equality used to arrive at the conclusion.
Let p: x=3
q:
There is q is conclusion is 
If we multiply by x on both sides then we get


Hence, the multiplication property of equality used to arrive at the conclusion.
Answer:A.The multiplication property of equality