Hi
Here is the Justification
Line 1 : 3p-(p+8) = 5p-7 [Given]
Line 2: 3p-p-8=5p-7 [ Applying distributive property]
Line 3: 2p-8=5p-7 [Simplifying like terms]
Line 4: -8=3p-7 [Subtraction property]
Line 5 -1=3p [Additive property](Add 7 on both sides]
Line 6 -1/3=p [Multiplicative inverse or division]
Line 7 p=-1/3 [Property of equality]
Thank you.