The alloy consists of 17 parts copper and 3 parts zinc. What is the mass of the alloy if it contains 28 kilograms less zinc than copper?

Let’s calculate how many parts of metals are in the alloy:
17 + 3 = 20 pieces.
Let’s calculate how many parts of copper are more than zinc:
17 – 3 = 14 pieces.
There is 14 parts more copper than zinc.
Let’s calculate how many kilograms of metal are in one piece:
28: 14 = 2 kilograms.
One part of the alloy contains 2 kilograms of metal.
Let’s calculate the mass of the entire alloy. Multiply the number of parts – 20 by the mass of one part – 2 kilograms:
20 * 2 = 40 kilograms.
The mass of the entire alloy is 40 kilograms.
Answer: the mass of the entire alloy is 40 kilograms.