19. It is known that A and B are reciprocal, C and D are reciprocal, and the absolute value of X is equal to 2. Find x2-(a+b)+CD | x |+(a+b) 201+(-CD) 2012. (10) 20. If 2x+y=5, find the value of algebraic expression -3(2x+y)(2x+y-4)+4x+2y. (5 points) 2 1,

The first-year students went down to Jianying Memorial Park under the guidance of four math teachers. Admission to the park is 20 yuan per person. There are two preferential schemes. Scheme A: Teachers and students will be charged at 7.5% discount. Scheme B: The leading teacher is free, and the students are charged 20% off. (12) (3) If there is a student, how much do you need for each of the two preferential schemes according to algebra? (4) When a=80, which scheme is preferred. (5) When a= 120, which scheme is preferred.