Determine the values of A & B

Fixed expenses are costs that do not change with the number of cars washed.

• Power washer rental: R300 per day
• Payment to brother Tommy: R50 per day

$$\text{Fixed expenses} = \text{R}300 + \text{R}50 = \text{R}350$$

John's fixed expenses per day are $\boxed{\text{R}350}$.

Total expenses consist of fixed expenses and variable expenses.

• Fixed expenses: R350 (from 2.1)
• Variable expenses: R4 per car Let $x$ be the number of cars washed.

$$\text{Expenses} = \text{Fixed expenses} + (\text{Variable cost per car} \times \text{Number of cars})$$ $$E(x) = 350 + 4x$$

The formula for expenses is $\boxed{E(x) = 350 + 4x}$.

A represents the income for 5 cars. John charges R120 per car.

$$A = 5 \text{ cars} \times \text{R}120/\text{car} = \text{R}600$$

B represents the expenses for 15 cars. Use the formula $E(x) = 350 + 4x$ from 2.2.

$$B = E(15) = 350 + 4(15)$$ $$B = 350 + 60$$ $$B = 410$$

The values are $\boxed{A = 600}$ and $\boxed{B = 410}$.