I need help with a polynomial-related assignment

A boy is building a pool .
To fit the dimensions of the various land spaces, he realizes that the length of the pool has to be three times the size of the width plus 3 and the depth has to be 7 less than twice the length.
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Task 1
Create expressions to represent the dimensions of the pool.
I have this (below)
Width = W, L = 3W + 3, D = 7 – 2L
Is that correct
1. Create a variable to represent the width of the pool. Determine the expressions to represent length and the depth in terms of the width

Question

I need help with a polynomial-related assignment

A boy is building a pool .
To fit the dimensions of the various land spaces, he realizes that the length of the pool has to be three times the size of the width plus 3 and the depth has to be 7 less than twice the length. 
________________________________________
Task 1
Create expressions to represent the dimensions of the pool.
I have this (below)
Width = W, L = 3W + 3, D = 7 – 2L
Is that correct
1.	Create a variable to represent the width of the pool. Determine the expressions to represent length and the depth in terms of the width