Simplify: (1) 6758 + 5648 (2) 24235 - 2445 (3) 10112 x H2 (4)

$$5_8 + 4_8 = 9_{10}$$

To convert $9_{10}$ to base 8, divide by 8: $9 \div 8 = 1$ with a remainder of 1. So, $9_{10} = 11_8$.
Write down 1 and carry over 1.

$$7_8 + 6_8 + 1_8 (\text{carry}) = 14_{10}$$

To convert $14_{10}$ to base 8, divide by 8: $14 \div 8 = 1$ with a remainder of 6. So, $14_{10} = 16_8$.
Write down 6 and carry over 1.

$$6_8 + 5_8 + 1_8 (\text{carry}) = 12_{10}$$

To convert $12_{10}$ to base 8, divide by 8: $12 \div 8 = 1$ with a remainder of 4. So, $12_{10} = 14_8$.
Write down 14.

Combining these results, we get:

$$\begin{array}{c} \quad \quad 1 \ 1 \quad (\text{carries}) \\ \quad 675_8 \\ + \ 564_8 \\ \hline \quad \mathbf{1461_8} \\ \end{array}$$

The final answer is $\boxed{1461_8}$.