The alloy ingot is 28% copper, 56% iron, and the remaining 144 g is nickel. What is the mass of the ingot?

Let us denote the mass of the ingot by x.

In the initial data for this task, it is reported that the ingot consists of 28% copper and 56% iron, therefore, the mass of copper in the ingot is (28/100) * x = 0.28x grams, and the mass of iron in the ingot is ( 56/100) * x = 0.56x gram.

Since the remaining 144 grams of the ingot is nickel, we can write the following equation:

0.28x + 0.56x + 144 = x,

solving which, we get:

0.84x + 144 = x;

x – 0.84x = 144;

0.16x = 144;

x = 144 / 0.16;

x = 900 g.

Answer: the weight of the ingot is 900 g.