a) \( 0,25=\frac{1}{x} \)

To solve for \( x \), you can start by rewriting the equation. Multiplying both sides by \( x \) gives you \( 0.25x = 1 \). Next, divide both sides by \( 0.25 \) to isolate \( x \). This simplifies to \( x = \frac{1}{0.25} \), which equals \( 4 \). So, the solution is \( x = 4 \)! Now, if you're wondering how to quickly convert decimals to fractions or the other way around, just remember that \( 0.25 \) equals \( \frac{25}{100} \), which simplifies to \( \frac{1}{4} \). Knowing this can be super handy in math problems where fractions and decimals are involved.