Can somebody lend a hand with some algebra? i'm in a jam and would greatly appreciate some !

Consider a cube that has sides of length l. now consider putting the largest sphere you can inside this cube without any point on the sphere lying outside of the cube. the volume ratio -volume of the sphere/ volume of the cube is 1. 5.2 × 10−1 2. 3.8 × 10−1 3. 1.9 4. 2.5 × 10−1 5. 3.8

If f(x)=x+7 and g(x)=1/x what is (fog)(x)

What is the perimeter of a rectangle if the length is 5 and the width is x?