I need help on this one and all the others please

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

Helll ! 1,400 tons of wheat of two different varieties was delivered to the silo. when processing one variety, there was 2% of waste and 3% during the processing of the second variety of wheat. after the processing, the amount of remaining wheat was 1,364 tons. how many tons of each variety of wheat was delivered to the silo?

8litres of paint can cover 129.6 m². how much paint is required to paint an area of 243m²?