Pleaseee help (working out not necessary)

Explain how you can use the associative property to evaluate (7x50)x4.

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

The difference of two numbers is 40. find the numbers if 0.3 parts of one number is equal to 37.5% of the other one.