The greatest common factor is simply w.
You need the total of square feet of the mural before you can divide 50 square feet to it and get your answer of how many pints of paint you will need.
For example.
Mural size is 2800 square feet
1 pint per 50 square feet
Work out problem.
2800 square feet ÷ 50 square feet= ?
= 56 pints of paint