Question

Помогите плиз!! СРОЧНО!!!

Answer 1

$1.;1);frac{0,4}{2,8}+frac27=frac{0,4}{7cdot0,4}+frac27=frac17+frac27=frac37\2);frac{2,1}{0,3}+frac{7,2}{0,9}=frac{7cdot0,3}{0,3}+frac{8cdot0,9}{0,9}=7+8=15\3);frac{5,6}{8}cdotfrac{3,5}{0,7}=frac{8cdot0,7}8cdotfrac{5cdot0,7}{0,7}=0,7cdot5=3,5\4);frac12-frac34:2=frac12-frac34cdotfrac12=frac12-frac38=frac48-frac38=frac18\5);frac{0,2}2cdot3,5=frac{0,2}{10cdot0,2}cdot3,5=frac{3,5}{10}=0,35$
$6);left(frac{7,8}{0,6}-4right)cdotfrac13=left(frac{10cdot0,6}{0,6}-4right)cdotfrac13=(10-4)cdotfrac13=6cdotfrac13=2\\2.;frac a{4,8-2,3}-frac a{3,5+2,5}=frac a{2,5}-frac a6=frac{12a}{30}-frac{5a}{30}=frac{7a}{30}\a=4frac34-2frac14=frac{17}4-frac{9}4=frac64=1frac24=1frac12\frac{7a}{30}=frac{7cdot1frac12}{30}=frac{7cdotfrac32}{30}=frac{7cdot3}{2cdot30}=frac{21}{60}=frac7{20}$