Write 12345678*10^{-10} as a decimal.
$10^{-10}=\frac{1}{10^{10}}$, so we have $12345678*10^{-10}=\frac{12345678}{10^{10}}$. But $10^{10}$ is 1 with 10 zeroes after it, so we have $\frac{12345678}{10^{10}}=\frac{12345678}{10000000000}$, which is equal to $\boxed{0.0012345678}$