Is this right? Can someone please check?

Answer: Yes, Substitution property is the correct option.
Step-by-step explanation:
Given: m∠A+m∠B =70° ...(i), m∠X=m∠A
Then, substitute m∠X for m∠A in (i) , we get
m∠X+m∠B =70°
So, the correct option is "Substitution property"