Given expression = 171 ÷ 19 x 9
= 171 / 19 x 9
= 9 x 9
= 81

Given expression = 108 ÷ 36 of 1/3 + 2/5 + 3³/₄
= 108 / 12 + 2 / 5 x 15 / 4
= 9 + 3 / 2
= 21 / 2
= 10¹/₂

Given expression = 8/5 - 2/3 x 13/12 + 7/5 x 1/3
= 8/5 - 13/18 + 7/15
= (144 - 65 + 42) / 90
= 121/90

Let 13/4 + 25/6 + N + 1/4 = 10, then
N = 10 - (13/4 + 25/6 + 1/4)
= 10 - (39 + 50 + 3)/12
= 10 - 92/12
= 7/3
= 2¹/₃

Given expression = 48/12 x (3/2 ÷ 1/2)
= 4 x (3/2) x 2
= 12

Given expression = 10 - [ 9 - {8 - 1}] - 5
= 10 - [9 - 7] - 5
= 10 - 2 - 5
= 3

Given expression = 1 + 1 ÷ {1 + 1 ÷ (1 + 1/3)}
= 1 + 1 ÷ { 1 + 1 ÷ 4/3}
= 1 + 1 ÷ { 1 + 3/4}
= 1 + 1 ÷ 7/4
= 1 + 1 x 4/7
= 1 + 4/7
= 1⁴/₇

Given expression = 3/2 x 4/3 + 1/4
= 2 + 1/4
= 9/4

Given expression = 1/2 + 1/2 ÷ 1/2
= 1/2 + 1
= 3 / 2

Let (17.28 ÷ N ) / (3.6 x 0.2) = 2
Then, 17.28 / N = 1.44
? N = 17.28 / 1.44
= 12