x + 21/40 = 53/40
x = 53/40 - 21/40
x = 32/40 = 4/5
34/35 : x = 17/5
x = 34/35 : 17/5
x = 2/7
`x + 3 / 4 xx 7 / 10 = 53 / 40`
`x + 21 / 40 = 53 / 40`
`x = 53 / 40 - 21 / 40`
`x = 32 / 40`
`x = 4 / 5`
____________________________
`( 2 / 5 + 4 / 7 ) : x = 17 / 5`
`( 14 / 35 + 20 / 35 ) : x = 17 / 5`
`34 / 35 : x = 17 / 5`
`x = 34 / 35 : 17 / 5`
`x = 34 / 35 xx 5 / 17`
`x = 2 / 7`
x + 3/4 x 7/10 = 53/40
x + 21/40 = 53/40
x = 53/40 - 21/40
x = 4/5
(2/5 + 4/7) : x = 17/5
34/35 : x = 17/5
x = 34/35 : 17/5
x = 2/7
\(x+\dfrac{3}{4}\times\dfrac{7}{10}=\dfrac{53}{40}\)
\(x+\dfrac{21}{40}\)
\(x=\dfrac{53}{40}-\dfrac{21}{40}\)
\(x=\dfrac{32}{40}\)
\(x=\dfrac{4}{5}\)
\(\left(\dfrac{2}{5}+\dfrac{4}{7}\right):x=\dfrac{17}{5}\)
\(\dfrac{34}{35}:x=\dfrac{17}{5}\)
\(x=\dfrac{34}{35}:\dfrac{17}{5}\)
\(x=\dfrac{34}{35}\times\dfrac{5}{17}\)
\(x=\dfrac{2}{7}\)