1.Найдите значение выражения : 8-4,2:(2 5\14-1 4\21)= 2.Решите уровнение: 1,2+3\10 y =8\15y+0,78

[latex]1)[/latex] [latex]8-4,2:(2 \frac{5}{14}-1 \frac{4}{21} )=8-4,2:(2 \frac{15}{42}-1 \frac{8}{42})=8-4,2:1 \frac{7}{42}= [/latex][latex]8-4,2:1 \frac{1}{6}=8- \frac{42}{10} * \frac{6}{7} =8- \frac{36}{10}=8-3,6=4,4 [/latex] [latex]2)[/latex] [latex]1,2+ \frac{3}{10}y= \frac{8}{15}y+0.78 [/latex] [latex] \frac{3}{10}y- \frac{8}{15}y=0.78 -1.2[/latex] [latex] \frac{9}{30}y- \frac{16}{30}y=-0.42[/latex] [latex]- \frac{7}{30}y=- \frac{21}{50} [/latex] [latex] \frac{7}{30}y= \frac{21}{50} [/latex] [latex]y= \frac{21}{50}* \frac{30}{7} [/latex] [latex]y= \frac{9}{5}[/latex] [latex]y=1.8[/latex] Ответ: [latex]1,8[/latex]

2 5/14-1 4/21 = 7/6 4 2/10=4 1/5:7/6=3 3/5=3,6 8-3,6=4,4 ====== 2. 3/10 у-8/15 у = 0,78-1,2 -7/30у=- 0,42=-42/100 у= 42/100:7/30=42/100*30/7=42*30/100*7=1,8