4. a) x * y * z =4/5 *5/6 = 4/6 = 2/3
b) 2/3 * 9/4 = 3/2
5. a) x(y-z) = xy - xz = 21/10 - 3/5 = 21/10 - 6/10 = 15/10 = 3/2
b) 7/6 -3/4 =14/12 - 9/12 = 5/12
