Question

I need help on this question

Answer 1

its the transitive property of equality.
Basically if a = b and b = c, then a = c

Answer 2

The transitive property is a fundamental mathematical axiom that states that if two variables or mathematical expresssions are equal to the same constant or variable, then the first two must be equal.

In simple words: \(a=z\) and \(b=z\) then \(a=b\).
or a more real-world example: if 100g of rice is 0.5$ on the store, and 1kg of flour is 0.5$ on another store, you would conclude that in regards of the market, 100g of rice is worth the same as 1kg of flour.

That's pretty much it, no magic involved.