What is 3x 5 3x 15?

The expression "3x 5 3x 15" appears to be a multiplication of terms. If we interpret it as (3x \times 5 \times 3x \times 15), then we can simplify it as follows: (3x \times 3x = 9x^2) and (5 \times 15 = 75). Thus, the overall expression simplifies to (9x^2 \times 75 = 675x^2).