Calculate Mrs. Ncube's monthly savings and total expenses based on her income and budget.

Her total income includes her monthly salary and the monthly housing subsidy.

$$\text{Total income} = \text{Monthly salary} + \text{Monthly housing subsidy}$$ $$\text{Total income} = \text{R}17\,415.39 + \text{R}900$$ $$\text{Total income} = \text{R}18\,315.39$$ $$\boxed{\text{R}18\,315.39}$$

Mrs Ncube saves 25% of her total monthly income from her employment.

$$\text{Monthly saving (A)} = 25\% \times \text{Total income}$$ $$\text{Monthly saving (A)} = 0.25 \times \text{R}18\,315.39$$ $$\text{Monthly saving (A)} = \text{R}4\,578.8475$$

Rounding to two decimal places:

$$\text{Monthly saving (A)} = \text{R}4\,578.85$$ $$\boxed{\text{R}4\,578.85}$$

Total monthly expenses (B) is the sum of all listed expenses in the budget table, including savings (A).

$$\text{Total expenses (B)} = \text{School fees} + \text{Groceries} + \text{Rent} + \text{Electricity and water} + \text{Entertainment} + \text{Savings (A)} + \text{Clothing and shoes} + \text{Fuel} + \text{Miscellaneous expenses}$$ $$\text{Total expenses (B)} = (\text{R}800 \times 2) + \text{R}1\,600 + \text{R}4\,200 + \text{R}1\,100 + \text{R}700 + \text{R}4\,578.85 + \text{R}1\,400 + \text{R}1\,200 + \text{R}1\,500$$ $$\text{Total expenses (B)} = \text{R}1\,600 + \text{R}1\,600 + \text{R}4\,200 + \text{R}1\,100 + \text{R}700 + \text{R}4\,578.85 + \text{R}1\,400 + \text{R}1\,200 + \text{R}1\,500$$ $$\text{Total expenses (B)} = \text{R}17\,878.85$$ $$\boxed{\text{R}17\,878.85}$$

She donates the balance to charity after all her expenses. The balance is her total income minus her total expenses (B).

$$\text{Amount donated to charity} = \text{Total income} - \text{Total expenses (B)}$$ $$\text{Amount donated to charity} = \text{R}18\,315.39 - \text{R}17\,878.85$$ $$\text{Amount donated to charity} = \text{R}436.54$$ $$\boxed{\text{R}436.54}$$