15. в) $$x - \frac{1}{4} = 1\frac{1}{4}$$

в) $$x - \frac{1}{4} = 1\frac{1}{4}$$ $$ x - \frac{1}{4} = \frac{5}{4}$$ $$ x = \frac{5}{4} + \frac{1}{4}$$ $$ x = \frac{6}{4}$$ $$ x = \frac{3}{2}$$ $$ x = 1\frac{1}{2}$$ Ответ: $$1\frac{1}{2}$$