... Challenge 5 Find the point-average of a student with A in mathe-matics, A in physics, B in chemistry, B in English, and C in history - using the scale: A, 5 points; B, 4 points; C, 3 points; ... obtained by replacing x in YI by ; ~ } . Let Y3 be the simplified expression obtained by replacing x in Y2 by ; ~ : ' and so forth. Find Y(h YIOO, YSOI' Challenge 1 Find ... especially interesting. More often, they are in the supporting cast, serving as the indispensable tool for expressing the data in a problem. Both roles are explored in this section. 5-1 Find the...