a) 1-y = $$\frac{7}{24}$$ + $$\frac{1}{4}$$;
1 - y = $$\frac{7}{24}$$ + $$\frac{6}{24}$$
1 - y = $$\frac{13}{24}$$
y = 1 - $$\frac{13}{24}$$
y = $$\frac{24}{24}$$ - $$\frac{13}{24}$$
y = $$\frac{11}{24}$$
Ответ: $$\frac{11}{24}$$