Fraction: divide the unit "1" into several parts on average, indicating such one or several parts, which is called a fraction. The basic nature of a fraction: the numerator and denominator of the fraction are multiplied or divided by the same number at the same time (except 0), and the size of the fraction remains unchanged. The properties of constant quotient: dividend and divisor expand or shrink by the same multiple at the same time, and the quotient remains unchanged. Decreasing score: when a score is equal to it, but the numerator and denominator are small, it is called lowering score. Comprehensive score: eight different denominator scores are converted into the same denominator score equal to the original score, which is called comprehensive score.