Basically you explain what your answer is and how you got it then you should be good!
Answer:
10 m
Step-by-step explanation:
Given:
The discharge of water is equal to the product of of its width, its average depth and its speed.
Let
be discharge of water,
be its width,
be its average depth and
be its speed.
So, 
As per question,

Plug in the above values and solve for
.

Therefore, the average depth of the Mississippi river is 10 m.
Answer:
In Expanded notation it is 
In numerals it is 6.05
Step-by-step explanation:
Expanded notation
Expanded notation is a helpful way to rewrite numbers in order to show the place value of each digit.
Normal number of we have
.........,Hundred, Tens ,Unit
eg. 1.) 514
5 = hundred place
1 = tens place
4= unit place
Now for decimal numbers
tenths,hundredths,thousandths........
eg. 1.) 0.25
0 = unit place
2 = tenths place 
5 = hundredths place 
We will have example in numerals and it expanded notation.
1.
6.05 ( six and five hundredths)
Expanded form

Here,
6 is in Unit place
0 is in Tenths place
5 is in Hundredths place
Well, instead of doing 3*3*3*3*3*3*3
You could just do