a = 7/3 - 4/3 : 5/2 = 9/5
A = 3/3 : 5/2 = 2/5
B = 7/3 - 3/4 x 2/5 = 61/30
C = 27/15 = 9/5
b = 3/4 - 5/4 x 1/2 = 1/8
A = -2/4 = -1/2
B = -2/8 = -1/4
C = 1/8 = 1/8
c = 1/9 + 1/6 = 5/18 ou environ 0,277
A = 2/15 = 2/15
B = 0,227 = 227/1000
C = 5/18 = 5/18
