a) 2/3 + 1/8 - 5/24
= 19/24 - 5/24
= 14/24
= 7/12
b) 1/3 + 2/5 - (2/5 + 1/6)
= 1/3 + 2/5 - 2/5 - 1/6
= (1/3 - 1/6) + (2/5 - 2/5)
= 1/6 + 0
= 1/6
c) 1$\frac{1}{4}$ - 0,25.(-3/8 + 1/6)
= 5/4 - 1/4.(-5/24)
= 5/4 - (-5/96)
= 5/4 + 5/96
= 125/96
d) 3/8 + 5/8 : (-15/16)
= 3/8 + 5/8 x (-16/15)
= 3/8 + (-2/3)
= 3/8 - 2/3
= -7/24