Converting 2,25 m to cm, the answer is

$$
2.25 \text{ m} \times 100 \frac{\text{cm}}{\text{m}} = 225 \text{ cm}
$$
$$
\boxed{225 \text{ cm}}
$$

    $$
    \text{Total Expenditure} = \text{R}18 + \text{R}25 + \text{R}20
    $$

    $$
    \text{Total Expenditure} = \text{R}63
    $$
    $$
    \boxed{\text{R}63}
    $$

*   **6.1.2. Surplus / left over / savings:**

    $$
    \text{Surplus} = \text{Income} - \text{Total Expenditure}
    $$
    $$
    \text{Surplus} = \text{R}90 - \text{R}63
    $$

    $$
    \text{Surplus} = \text{R}27
    $$
    $$
    \boxed{\text{R}27}
    $$

*   **6.1.3. How much percentage did she spent?**

    $$
    \text{Fraction spent} = \frac{\text{Total Expenditure}}{\text{Income}} = \frac{\text{R}63}{\text{R}90}
    $$

    $$
    \text{Percentage spent} = \frac{63}{90} \times 100\%
    $$
    $$
    \text{Percentage spent} = 0.7 \times 100\%
    $$
    $$
    \text{Percentage spent} = 70\%
    $$
    $$
    \boxed{70\%}
    $$

$$
\text{Total cool drink needed} = 30 \text{ friends} \times 200 \frac{\text{ml}}{\text{friend}} = 6000 \text{ ml}
$$

$$
\text{Number of bottles} = \frac{\text{Total cool drink needed}}{\text{Volume per bottle}} = \frac{6 \text{ litres}}{2 \frac{\text{litres}}{\text{bottle}}}
$$
$$
\text{Number of bottles} = 3 \text{ bottles}
$$
$$
\boxed{3 \text{ bottles}}
$$