Решим уравнение:
$$0.5(\frac{1}{4}y + 2.1) = -0.5y - 3\frac{1}{4}$$
$$0.125y + 1.05 = -0.5y - 3.25$$
$$0.125y + 0.5y = -3.25 - 1.05$$
$$0.625y = -4.3$$
$$y = \frac{-4.3}{0.625}$$
$$y = -6.88$$
Ответ: y = -6.88