3/16 - 9/24 =
Numitor comun : 2^4•3=48
16=2^4
24=2^3•3
(3•3-9•2)/48 = -9/48 = -3/16
-7/9 + 8/10 =
Numitor comun : 2•3^2•5=90
9=3^2
10=2•5
(-7•10+8•9)/90 = 2/90 = 1/45
-11/12 - 7/5 =
Numitor comun : 2^2•3•5=60
12=2^2•3
5=1•5
(-11•5-7•12)/60 = (-55-84)/60 = (-139)/60