Use the commutative property of multiplication to write a related nunber sentence

This is about circle theorems. someone asap : (

Which expression is equal to (21)(7)(3x) using the associative property? (21 · 7 · 3)x (7)(21)(3x) 32(7 + 3x) (3x)(7)(21)

Talia took the bus from her home to the bank and then walked back to her home along the same route. the bus traveled at an average speed of 40 km/h and she walked at an average speed of 5 km/h. to determine the time, x, that it took talia to walk home, she used the equation 40(0.9 – x) = 5x. the time of trip 2 is hours. the distance of trip 1 is km.