## Algebra 1: Common Core (15th Edition)

$7 × 10^3 + 1 × 10^2+2×10^1+5×10^0$
$7125$ is the same thing as $7000 + 100+20+5$, which is $7×1000+1×100+2×10+5×1$ $1000$ is $10^3$, $100$ is $10^2$, $10$ is $10^1$ and $1$ is $10^0$, so the answer is $$\boxed{7 × 10^3 + 1 × 10^2+2×10^1+5×10^0}$$