5. a = 7/3 + 1/4 x 5/3 = 7/3 + 5/12 = 28/12 + 5/12 = 33/12 = 11/4
b = 4/7 x 3 + 1/2 = 12/7 + 1/2 = 24/14 + 7/14 = 31/14
E = 1/2 + 2x11/4 -3x31/14
E = 1/2 + 11/2 - 93/14
E = 12/2 - 93/14
E = 6 - 93/14 (amplifici pe 6 cu 14)
E = 84/14 - 93/14
E = -9/14
6. ax(bxc) = axbxc = 3/7 x 14/15 = 2/5
