Let's denote the mass of the crate as $m$. Since we are given that the crate carrying 50 identical balls weighs 28.3 kg and each ball weighs 0.54 kg, we can set up the equation: $$ m + 50 \cdot 0.54 = 28.3.$$ Simplifying the equation, we have $$m + 27 = 28.3.$$ Subtracting 27 from both sides, we get $$m = 28.3 - 27 = 1.3.$$ Therefore, the mass of the crate is 1.3 kg.
