We have the difference between 30 and x(our unknown value) is equal to 17; so we just simply set it up that way. Always think of x or any variable(like in your question they use p, it can be anything u want, it’s simply a representation of an unknown value we are trying to find)as your unknown and what operation they are implying as in this case it’s subtraction as they want the difference between 30 and x.
So the answer is a. 30-p=17
Hope this helped and any questions please just ask. Thank you!
