Question

y × 5/7 - 5/7 + 3/4 = 21/28

Answer 1

\(\dfrac{5}{7}y-\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{21}{28}\)

\(\Rightarrow\dfrac{5}{7}y-\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{3}{4}\)

\(\Rightarrow\dfrac{5}{7}y=\dfrac{3}{4}+\dfrac{5}{7}-\dfrac{3}{4}\)

\(\Rightarrow\dfrac{5}{7}y=\dfrac{5}{7}\)

\(\Rightarrow y=1\)

Answer 2

Ta có: \(y\cdot\dfrac{5}{7}-\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{21}{28}\)

\(\Leftrightarrow y\cdot\dfrac{5}{7}-\dfrac{5}{7}=0\)

hay y=1