Well, from the first row to the second you added +7 on both sides. On the other rows you merely did some arithmetic.
Usually one gets from the first line to the last one directly :)
Provide an attachment so we can assist you.
For the order of operation use PEMDAS
Parenthesis
Exponent
Multiplication
Division
Addition
Subtraction
For memorizing the order you could say
Please
Excuse
My
Dear
Aunt
Sally
Answer:

Step-by-step explanation:
The Cylindrical coordinates are:
x = rcosθ, y = rsinθ and z = z
From the question, on the xy-plane;


where:
0 ≤ r ≤
and 0 ≤ θ ≤ 2π
∴











