n, 123.456 + 456.321 - 256.444

=  (123.456 + 456.321) - 256.444
= 456.(123 + 321) - 256.444

= 456.444 - 256.444

= 444.( 456 - 256)

= 444. 200

= 88800

m, 113.38 + 113.62 + 87.62  + 87.38

= (113.62 + 87.62) + (113.38 + 87.38)

= 62.(113 + 87) + 38.( 113 + 87)

= 62.120 + 38. 120

= 120.(62 + 38)

= 120.100

= 12000
 

l, 37.7 + 80.3 + 43.7

= (37.7 + 43.7) + 80.3

= 7.(37 + 43) + 80.3

= 7.80 + 80. 3

= 80.(7 + 3)

= 80.10

= 800

k, 32.47 + 32.53 

= 32.(47 + 53)

= 32. 100

= 3200

i, 36.28 + 36.82 + 64.69 + 64.41

= (36.28 + 36.82) + (64.69 + 64.41)

= 36.(28 + 82) + 64.(69 + 41)

= 36. 110 + 64 .110

= 110.(36 + 64)

= 110.100

= 11000

h, 39.8 + 60.2 + 21.8

= (39.8 + 21.8) + 60.2

= 8.(39 + 21) + 60.2

= 8.60 + 60.2

= 60.(8 + 2)

= 60.10

= 600

g, (2100 - 42): 21

= 2100 : 21 - 42: 21

= 100 - 2

= 98

e, 12.53 + 53.172 - 53.84

= 53.(12 + 172 - 84)

= 153.( 184 - 84)

= 153. 100

= 15300

d, (1200 + 60):12

= 1200: 12 + 60: 12

= 100 + 5

= 105

c, 3.25.8 + 4.37.6 + 2.38.12

= (3.8).25 + (4.6).37 + (2.12).38

= 24.25 + 24.37 + 24.38

= 24.(25 + 37 + 38)

= 24.100

= 2400