Fractions must share a common denominator in order to be added or subtracted. The common denominator is the least common multiple of all the denominators.

To raise a term with an exponent to another exponent, retain the base and multiply the exponents: (x²)³ = x^(2x3) = x⁶

Percentages are ratios of an amount compared to 100. The percent change of an old to new value is equal to 100% x \({ new - old \over old }\).