a. 28 * 63
28 (60) + 28 (3) or 20 (60) +20 (3) + 8 (60) + 8 (3)
1680 + 84=1764 1200 / 60 +480 +24=1764
b. 17(59)
17 (50) + 17 (9) or 10 (50) + 10 (9) + 7 (50) +7 (3)
850 + 153=1003 500 + 90 + 63 =1003
c.458 (15)
458 (10) +458 (5) or 10 (400) + 10 (50) + 10 (8) + 5 (400) +5 (50) + 5 (8)
4580 +2290 = 6870 400 + 500 + 80 + 2000 + 250 + 40 = 6870
My work is kinda confusing but hope it helped