book Maths Puzzle Numerical Ability

explain how to work this problem
2x 4y- 3(7x -2y)

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book Other Question

An electric hoist is used to lift a piece of equipment. The diameter of the drum on the hoist is 10 inches, and the equipment must be raised 1 foot. Find the number of degrees through which the drum must rotate. No matter how I try, I am not understanding this type of problem....
3x -2y + 5z
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2y -3x -5z

This is how I try....
3x (3x-2y + 5z) -(2y + 5z)
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