c)
47 g + 6 dg =dg
47 g = 470 dg
470 dg + 6 dg = 476 dg
426 g + 3 cg=mg
426 g = 426 000 mg
3 cg = 30 mg
426 000 mg + 30 mg = 426 030 mg
15 dg + 17 mg =mg
15 dg = 1 500 mg
1 500 mg + 17 mg = 1 517 mg
21 dg - 30 cg =mg
21 dg = 2 100 mg
30 cg = 300 mg
2 100 mg - 300 mg = 1 800 mg