completează castele

Răspuns:
Explicație pas cu pas:...................................
a + b = 5/6 + 2/9 = (15 + 4)/18 = 19/18
a - b = 5/6 - 2/9 = (15 - 4)/18 = 11/18
b = 3 - 13/6 = (18 - 13)/6 = 5/6
a - b = (13 - 5)/6 = 8/6 = 4/3
b = 7/8 - 1/2 = (7 - 4)8 = 3/8
a + b = (7 + 3)/8 = 10/8 = 5/4
a = 2 - 3/10 = (20 - 3)/10 = 17/10
a - b = (17/10 - 3/10) = 14/10 = 7/5
a = 2/3 + 13/12 = (8 + 13)/12 = 21/12 = 7/4
a + b = (21+ 13)/12 = 34/12 = 17/6