1. (2+3/5) : (2/5-1/9)
= 13/5 : 13/45
= 9
2. (1+1/11) . (1+1/12) . (1+1/16)
= 12/11 . 13/12 . 17/16
= 13/11 . 17/16
= 221/176
3. 20,7 + 1,47 : 7 - 0,23 - 5
= 20,7 + 0,21 - 0,23 - 5
= 20,91 - 0,23 - 5
= 20,68 - 5
=15,68
4. 1 4/5 . 7/18 + 4/29 : 5/58 - 1 3/10
= 14/45 + 8/5 - 1 3/10
= 86/45 - 1 3/10
= 29/18