For terminating decimals: Count the decimal places, then write the number over the corresponding power of 10. For example, 0.75 = 75/100 = 3/4.
For repeating decimals: Use algebra. If x = 0.333..., then 10x = 3.333... Subtracting: 9x = 3, so x = 3/9 = 1/3.
For irrational numbers: Numbers like π (3.14159...) and √2 cannot be expressed as exact fractions. We provide the closest rational approximation.