First, distribute the -2 to the p and +1 in the parentheses.
9-2(p+1)=4(p-8)
9-2p-2=4(p-8)
Then on the other side do the same thing distributing the 4 to the p and -8.
9-2p-2=4(p-8)
9-2p-2=4p-32
Now isolate the variable p by adding 2p to each side
9-2p-2=4p-32
9-2=6p-32
From here you subtract 9 from 2 and then add 32 to both sides.
7=6p-32
39=6p
finally you divide both sides by 6 to get p.
39/6=p
6.5=p