Use mental math to determine the value of 15/124 x 230/30 ÷230/124

We can usually simplify in the head.  Start with the difficult ones, like 230 and 124.

15/124 x 230/30 ÷230/124
We see that the first 124 is a denominator, and after flipping the division, 124 is at the top, so they cancel out.
Similarly, 230 is a numerator and after flipping the division, 230 is a denominator, so again they cancel out.

We then collect only terms that remain, namely
15/30 which simplifies to half, or 1/2.