The image contains various problems related to fractions and arithmetic operations. I'll provide solutions and explanations for the questions presented.

1. Begin by rewriting the fractions with a common denominator:

1a) $\frac{1}{2} + \frac{7}{8}$

• Common denominator: 8.
• $\frac{1}{2} = \frac{4}{8}$, so: $\frac{4}{8} + \frac{7}{8} = \frac{11}{8}.$

1b) $\frac{3}{4} - \frac{2}{5}$

• Common denominator: 20.
• ( \frac{3}{4} = \frac{15}{20} \