-5/12+3/8
-3/5+2/5
7/15+[-2/5]
-1/8+3/8
1) -5/12 + 3/8 = (-5*2 + 3*3)/24 = -1/24.
2) -3/5 + 2/5 = (-3+2)/5 = -1/5.
3) 7/15 +(-2/5) = (7+(-2)*3)/15 = 1/15.
4) -1/8 + 3/8 = (-1+3)/8 = 2/8 = 1/4.