To get the answer you cancel out the minus of the negative 20 and change it to adding 20. then you subtract the 20 on both sides to get 3p=50-20. that would give you 3p= 30. then you would divide by 3 on both side. 3p/3=30/3. the 3 on 3p would cancel out so you will get p=30/3. the answer is p=10.
