Do the inverse operation:
P(x)+(3x-7)=0
P(x)=-3x+7
So first, you want to open the parenthesis here.
So, to do that, first look at the symbol before the parenthesis.
In this case it's a -.
So when it's a -, reverse the symbol inside the parenthesis. (This is because if you don't you're subtracting 2x and then adding 8, when really you're subtracting both 2x and 8.)
So,
9x - 2x - 8
Or simplified,
7x - 8
