Answer:
As a general rule to solve the problem we are going to transform all values to the lower unit.  
a. 3 km 9 hm 9 dam 19 m + 7 km 7 dam
  3,000 m 900 m 90 m 19 m + 7,000 m 70 m = 4,009 + 7,070 = 11,079 m 
  b. 5 sq.km 95 ha 8,994 sq.m + 11 sq. km. 11 ha 9,010 sq. m.
  5,000,000 sq m 95,0000 sq m 8,994 sq m + 11,000,000 sq m 110,000 sq
9,010 sq m
  5,103,994 sq m + 11,119,010 sq m = 16,223,004 sq m 
 c. 44 m – 5 dm
  44 m - 0.5 m = 43.5 m 
 d. 73 km 47 hm 2 dam - 11 km 55 hm

  73,000 m 4,700 m 20 m - 11,000 m 5,500 m 
77,720 m - 16,500 m = 61,220 m