a) 1/2 + 2/3 * 9/4 = = 1/2 + 3/2 = 4/2 = 2 .
b) 1/12 + 4/5 * 6 = 5+288/60 = 293/60
c) 2*4/9+2 = 8/9 + 2 = 16+ 36/ 18 = 52/18 = 26/9 .
d) = 3+14/12 - 15/34 + 3/2 (7-1/21) =...= 35+24/56 = 59/56 .
e) 12,9+1,8*7 = 12,9 + 12,6 = 25,5
f) 3+37:(1,8+0,(6)) = 3+37/162+60/0 = 3 + 37 * 222/90 = 2768/30 = 1384/15