Please help! I've been struggling with this question I don't get it at all.

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

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

What is 1/3x5 on anuber line what does it look like on a number line