The claim is incorrect. Treating the planets as basic spheres, the formula of the volume of a sphere states that volume = (4/3)(pi*r^3), where r is the radius. Since r is raised to the power of three, then doubling the radius would result in a volume that is 8 times larger than the original.
Can't see the question :/
Given:7-x-5=x+2
1)combine like terms
2-x=x+2
2)Isolate the variable
-x=x+2-2
3)move x to the left
-x-x=0
4)combine like terms
-2x=0
5)Divide
X=0