4.
[tex]\it a)\ \ \dfrac{1}{2}+2\cdot(0,25+3)=0,5+2\cdot3,25=0,5+6,5=7[/tex]
[tex]\it b)\ \ 0,6+\dfrac{3}{5}:1,2+2^{-1}\cdot\dfrac{2}{5}=0,6+0,6:1,2+\dfrac{1}{2}\cdot\dfrac{2}{5}=0,6+6:12+0,5\cdot0,4=\\ \\ =0,6+0,5+0,2=1,3[/tex]
5.
[tex]\it b)\ \ \dfrac{28}{31}\cdot\Big[4^{-1}+\Big(2\dfrac{1}{2}-\dfrac{7}{4}\Big):\dfrac{7}{8}\Big]=\dfrac{28}{31}\cdot\Big[\dfrac{1}{4}+\Big(\dfrac{10}{4}-\dfrac{7}{4}\Big):\dfrac{7}{8}\Big]=\\ \\ \\ = \dfrac{28}{31}\cdot \Big(\dfrac{1}{4}+\dfrac{3}{4}\cdot\dfrac{8}{7}\Big)=\dfrac{28}{31}\cdot \Big(\dfrac{^{7)}1}{\ 4}+\dfrac{24}{28}\Big)=\dfrac{28}{31}\cdot\dfrac{31}{28}=1[/tex]
