Which expression equals a number that is NOT a rational number?

The expression that equals a number that is NOT a rational number is 3π · 3³ / 7π.

Here’s the explanation:

1. 3π · 3³ / 7π simplifies to (3³/7) because the π cancels out. Since 3³ is a rational number (27), but it is divided by 7, the result is still rational.

2. All the other expressions are rational numbers:

– -18 / 5 is a rational number.

– 5 / 3 – 7 – 9 simplifies to a rational number.

– 3 · 3³ / 7 as well simplifies to a rational number.

However, the confusion often lies in the mixed numbers. Since all provide rational outcomes, but particularly the use of π in the first choice makes it non-rational.

Thus, the final answer is 3π · 3³ / 7π, as it involves π, which is irrational.

If you have further questions or need more assistance, feel free to ask!