Question

пешиииите пжжжжжж очень надо ​

Answer 1

1)

$\frac{x}{4} +3=7\\x+12=28\\x=16$

2)

$\frac{7}{20} x-\frac{5}{12} =\frac{2}{3} -\frac{1}{5} x\\21x-25=40-12x\\33x=65\\x=\frac{65}{33} =1\frac{32}{33}$

3)

$\frac{5}{x+5} =\frac{1}{5} \\x+5=25\\x=20$

4)

$\frac{(0,5+\frac{1}{4})\times2,1 }{(8,8-8\frac{3}{5}):\frac{2}{3}} =\frac{(0,5+0,25)\times2,1}{(8,8-8,6):\frac{2}{3} } =\frac{0,75\times2,1}{0,2:\frac{2}{3} } =(\frac{75}{10} \times\frac{21}{10} ):(\frac{2}{10} \times\frac{3}{2} )=\\=\frac{75}{10} \times\frac{21}{10} \times\frac{10}{3} =\frac{75}{10} \times7=\frac{15}{2} \times7=\frac{105}{2}=52,5$