1a) 195:[12.(13^2 - 80 : 2) - 69]
= 195:[12.(169 - 40) - 69]
= 195:[12.(129) - 69]
= 195:[1548 - 69]
= 195:1479
≈ 0.1317

1b) 72.13+28.5+72.17+28.25
= 936 + 1428 + 1224 + 706
= 4294

1c) 65.111-13.15:37
= 7205 - 3.405
= 7205 - 1215
= 5990

2a) (x:15-10).23-160=300
(x/15 - 10).23 - 160 = 300
(x/15 - 10).23 = 460
x/15 - 10 = 20
x/15 = 30
x = 450

2b) x-13-3.x+14=54
x - 13 - 3x + 14 = 54
-2x + 1 = 54
-2x = 53
x = -53/2

2c) 1000.[50-(2^x - 6)] = 4^2 + 3^2
1000.(50 - (2^x - 6)) = 16 + 9
1000.(50 - 2^x + 6) = 25
1000.(56 - 2^x) = 25
56000 - 1000.2^x = 25
1000.2^x = 55975
2^x = 55.975
x ≈ 5.807