Question

Помогите пожалуйста по математики 6 класс тема ПРОПОРЦИЯ

Answer 1

$\displaystyle \tt 2). \ \ \frac{4}{1,6}=\frac{7x-2}{10,4}\\\\. \ \ \ \ \ 10,4\cdot 4=1,6\cdot (7x-2)\\\\. \ \ \ \ \ 11,2x-3,2=41,6\\\\. \ \ \ \ \ 11,2x=44,8\\\\. \ \ \ \ \ x=4;\\\\\\4). \ \ \frac{3x+0,8}{9,6}=\frac{4,8}{3,6}\\\\. \ \ \ \ \ \frac{3x+0,8}{9,6}=\frac{4}{3}\\\\. \ \ \ \ \ 3\cdot(3x+0,8)=4\cdot 9,6\\\\. \ \ \ \ \ 9x+2,4=38,4\\\\. \ \ \ \ \ 9x=36\\\\. \ \ \ \ \ x=4;$

$\displaystyle \tt 6). \ \ \frac{8}{20}=\frac{28}{9x+7}\\\\. \ \ \ \ \ \frac{2}{5}=\frac{28}{9x+7}\\\\. \ \ \ \ \ 2\cdot (9x+7)=28\cdot 5\\\\. \ \ \ \ \ 18x+14=140\\\\. \ \ \ \ \ 18x=126\\\\. \ \ \ \ \ x=7;$