Answer
$1 × 10^3 + 2 × 10^2+5×10^1+4×10^0$
Work Step by Step
$1254$ is the same thing as $1000 + 200+50+4$, which is
$1×1000+2×100+5×10+4×1$
$1000$ is $10^3$, $100$ is $10^2$, $10$ is $10^1$ and $1$ is $10^0$, so the answer is
$$\boxed{1 × 10^3 + 2 × 10^2+5×10^1+4×10^0}$$
