a) $-1/3 + 7/3 = (-1+7)/3 = 6/3 =2$
b) $3/5 + -1/3 =9/15 + -5/15 = (9-5)/15 = 4/15$
c) $-2/13 + -11/26= -4/26 + -11/26 = (-4-11)/26 = -15/26$
d) $-2 + -5/8 = -16/8 + -5/8 = (-16-5)/8 = -21/8 $
e) $18/24 + 35/-10 = 3/4 - 7/2 = 3/4 - 14/4 = (3 -14)/4= -11/4$
f) $-8/14 + -45/54 = -4/7 - 5/6 = -24/42 - 35/42 = (-24-35)/42 = -59/42$
g) $3/2 + -3/5 + 1/4 = 30/20 + -12/20 + 5/20 = (30 - 12 +5)/20 = 23/20$