Answer:
I think its would be d
Step-by-step explanation:
the distributive property
I am not sure but I would say either step 2 or 4 but I am not 100% sure I hope you do well. Good Luck:)
Answer: 10
<u>Step-by-step explanation:</u>
varies directly means: 
Step 1: solve for k ⇒ 
Step 2: plug in the given value and k to solve for the missing value: 
42(5) = 21(x)

2(5) = x
10 = x