Question

Решите уравнения:

а) x + 4/15 = 2/3 + 2/5

б) ( 4/5 - x ) + 13/20 = 25/30

в) y – 5/20 = 5/8 – 3/10

г) 2/3 – ( 7/9 – а ) = 1/3

Answer 1

$x + frac{4}{15} = frac{2}{3} + frac{2}{5} \ \ x = frac{2}{3} + frac{2}{5}- frac{4}{15} \ \ x = frac{2*5+2*3-4}{15}=frac{10+6-4}{15}=frac{12}{15}= frac{4}{5}$

$( frac{4}{5} - x ) + frac{13}{20} = frac{25}{30} \ \ x = frac{4}{5} + frac{13}{20}-frac{25}{30} \ \ x = frac{4*12+13*3-25*2}{60}=frac{48+39-50}{60}=frac{37}{60}$

$y - frac{5}{20} = frac{5}{8} - frac{3}{10} \ \ y - frac{1}{4} = frac{5}{8} - frac{3}{10} \ \ y = frac{5}{8} - frac{3}{10}+frac{1}{4} \ \ y =frac{5*5-3*4+1*10}{40}=frac{25-12+10}{40}=frac{23}{40}$

$frac{2}{3} -( frac{7}{9} - a ) = frac{1}{3} \ \ frac{2}{3} - frac{7}{9} + a = frac{1}{3} \ \ a = frac{1}{3} -frac{2}{3}+frac{7}{9} \ \ a = frac{1*3-2*3+7}{9}=frac{3-6+7}{9}= frac{4}{9}$