a)
6m2 58dm2 = 6m2 + 58100m2 = 658100m2
19m2 7dm2 = 19m2 + 7100m2 = 197100m2
43dm2 = 43100m2
b)
9cm2 58mm2 = 9cm2 + 58100cm2 = 58100cm2
15cm2 8mm2 = 15cm2 + 58100cm2 = 58100cm2
48mm2 = 48100cm2