[latex]7\cdot(x+8)=84\\\\7\cdot x+7\cdot 8=84\\\\7x+56=84\ \ \ \ /-56\\\\7x=28\ \ \ \ /:7\\\\x=28:7\\\\x=4[/latex]

x=4 as: 7(x+8)=84 simplifies to 7x+56=84 Then: 7x+56-56=84-56 simplifies to 7x=28 Then: 7x/7=28/7 simplifies to x=4