My father's desk is 3 300 mm long and mine measures 6 200 mm How much longer is my desk than my father's desk? Write down your answer in m and cm, and then in m.

$$9 \text{ m} - 3.5 \text{ m} = 5.5 \text{ m}$$

The amount of ribbon left is $\boxed{5.5 \text{ m}}$.

Since $1 \text{ m} = 1000 \text{ mm}$ and $1 \text{ cm} = 10 \text{ mm}$:

$$2900 \text{ mm} = 2 \text{ m } 90 \text{ cm}$$

$$2900 \text{ mm} = \frac{2900}{1000} \text{ m} = 2.9 \text{ m}$$

My desk is $\boxed{2 \text{ m } 90 \text{ cm}}$ or $\boxed{2.9 \text{ m}}$ longer than my father's desk.

$$90 \text{ m} - 19.5 \text{ m} = 70.5 \text{ m}$$

The amount of wool left is $\boxed{70.5 \text{ m}}$.

$$1520 \text{ km} - 579 \text{ km} = 941 \text{ km}$$

Sipho drove $\boxed{941 \text{ km}}$.

$$2871 \text{ km} - 1264 \text{ km} = 1607 \text{ km}$$

There are $\boxed{1607 \text{ km}}$ left before the car needs to go for service.