Решение:
а) \((z-6)\cdot \frac{3}{7}=3\)
\(z-6=3:\frac{3}{7}\)
\(z-6=3\cdot \frac{7}{3}\)
\(z-6=7\)
\(z=7+6\)
\(z=13\)
Ответ: 13
б) \(5\frac{1}{4}y-5\frac{1}{4}=5\frac{1}{4}\)
\(\frac{21}{4}y=\frac{21}{4}+\frac{21}{4}\)
\(\frac{21}{4}y=\frac{42}{4}\)
\(y=\frac{42}{4}:\frac{21}{4}\)
\(y=\frac{42}{4}\cdot \frac{4}{21}\)
\(y=2\)
Ответ: 2