a) 2$\dfrac{1}{2}$ - $\dfrac{4}{3}$ + ($\dfrac{-1}{3})^{4}$
= $\dfrac{5}{2}$ - $\dfrac{4}{3}$ + $\dfrac{1}{81}$
= $\dfrac{7}{6}$ + $\dfrac{1}{81}$
= $\dfrac{191}{162}$
b) 15$\dfrac{1}{4}$ : ($\dfrac{-5}{7}$) - 25$\dfrac{1}{4}$ : ($\dfrac{-5}{7}$)
= 15$\dfrac{1}{4}$ . ($\dfrac{-7}{5}$) - 25$\dfrac{1}{4}$ . ($\dfrac{-7}{5}$)
= $\dfrac{-7}{5}$ . (15$\dfrac{1}{4}$ - 25$\dfrac{1}{4}$)
= $\dfrac{-7}{5}$ . (-10)
= 14
c) $\sqrt[]{0,16}$ - $\sqrt[]{\dfrac{1}{25}}$
= 0,4 - $\dfrac{1}{5}$
= $\dfrac{1}{5}$
d) 4 . ($\dfrac{-1}{2}$) . 3 + $\dfrac{1}{2}$ . 5
= -2 . 3 + $\dfrac{5}{2}$
= -6 + 2,5
= -3,5
