Question

помогите пожалуйста срочно ​

Answer 1

$\displaystyle 1)3a-5a+2a-8a=(3-5+2-8)a=-8a\\\\ 2)2m-8,5n-14m+9n=-12m-8,5n+9n=-12m+0,5n\\\\ 3)-\frac{2}{5}c+\frac{1}{3}b+\frac{4}{7}c=\frac{-2c*7+4c*5}{35}+\frac{1}{3}b=\frac{-14c+20c}{35}+\frac{1}{3}b=\\ \\ \frac{6c}{35}+\frac{1}{3}b$