\(\frac{1}{3}+\frac{2}{3}-\frac{1}{4}\div y=\frac{75}{100}\)
\(\Leftrightarrow\frac{3}{3}-\frac{1}{4}\div y=\frac{3}{4}\)
\(\Leftrightarrow\frac{1}{4}\div y=\frac{3}{3}-\frac{3}{4}\)
\(\Leftrightarrow\frac{1}{4}\div y=\frac{3}{12}\)
\(\Leftrightarrow y=\frac{1}{4}\div\frac{3}{12}\)
\(\Leftrightarrow y=1\)