7) -5/6 : 35/42 = -5/6 x 42/35
= $\frac{-5.42}{6.35}$
= $\frac{-5.7.6}{6.7.5}$
= -1
8) -8/18 - 15/27 + 1/2 = -1 + 1/2
= -2/2 + 1/2
= -1/2
9) 3/5 - 4/3 + (-3/4) = 3/5 - 4/3 - 3/4
= -11/15 - 3/4
= -89/60
10) 1/2 - (1/3 + 1/10) = 1/2 - 1/3 - 1/10
= (1/2 - 1/10) - 1/3
= 2/5 - 1/3
= 1/15
11) 3/4 + (-5/2) + (-3/5) = 3/4 - 5/2 - 3/5
= (-7/4) - 3/5
= -47/20
12) 1/6 + 1/2 + 1/3 - 1 = 2/3 + 1/3 - 1
= 3/3 - 1
= 1 - 1
= 0
