korrinevbrulz7582 korrinevbrulz7582 20-12-2020 Mathematics contestada 3. Evaluate each expression. (total 6 marks: half mark for showing steps, half for correct answer.) a) 7x when x=4 b) 9-2y when y=3 c) 5x+8 when x=9 e) 2r -21 when r=15 f) 3-4y when y=5 f) w+20 when w=4