The goal is to isolate the variable p, right?
Lets write this out:
3/7 p = -6
We need to move 3/7 to the other side so that p can be isolated, lets do that.
3/7 ÷ 3/7 p = -6 ÷ 3/7
How does this work? Why did I do it to both sides?
When I divided 3/7 by 3/7 they canceled out, because whenever you divide something by itself it equals 1.
I divided -6 by 3/7 because because there is an equal sign, and a rule of thumb is that whatever you do on one side of the equation, you do to the other.
Now we have the equation:
p = -6 ÷ 3/7
therefore p = -14
Hope I was of use.
Cheers,