Someone please check my answers

Question

1.In the number 854,263,189 what number tells the number of millions.
4

2.Write 4x4x4x4x4 as a power of 4
4^5

3.write 684 in expanded form
600+80+4

4.Turner agrees to buy a boat for $2,800 down and $129 a month for 48 months. What is the total cost of the boat?
$8,992

5.72/8-9/3=
6

Answer 1

#1: correct
#2: correct
#3: im not sure but i think its incorrect
#4: incorrect
#5: correct

Answer 2

Turner agrees to buy a boat for $2,800 down and $129 a month for 48 months. What is the total cost of the boat?

Answer 3

4 in 427,083