б) 5 1/4y – 5 1/4 = 4;

б) Решим уравнение:

$$ 5\frac{1}{4}y - 5\frac{1}{4} = 4 $$ $$ \frac{21}{4}y - \frac{21}{4} = 4 $$ $$ \frac{21}{4}y = 4 + \frac{21}{4} $$ $$ \frac{21}{4}y = \frac{16}{4} + \frac{21}{4} $$ $$ \frac{21}{4}y = \frac{37}{4} $$ $$ y = \frac{37}{4} : \frac{21}{4} $$ $$ y = \frac{37}{4} \cdot \frac{4}{21} $$ $$ y = \frac{37}{21} $$ $$ y = 1\frac{16}{21} $$

Ответ: 1 16/21