### Solution
Let's carefully address each part of the question by interpreting the given data and incorporating the given information step-by-step.
#### 1.1 Determine the selling price of ONE photograph.
To find the selling price of one photograph, we look at the income data provided in the table for a known number of photographs. For example, at 50 photographs, the income is 2500 rand (from the given table). Therefore, the selling price per photograph is calculated as:
[tex]\[ \text{Selling price per photograph} = \frac{\text{Total income for 50 photographs}}{\text{Number of photographs}} = \frac{2500 \text{ rand}}{50} = 50 \text{ rand} \][/tex]
So, the selling price of one photograph is 50 rand.
#### 1.2 Write down the formula that could be used to calculate the total income received.
Based on the provided table and the selling price per photograph, the total income can be calculated as:
[tex]\[ \text{Total income} = \text{Selling price per photograph} \times \text{Number of photographs} \][/tex]
Given the selling price per photograph from 1.1 is 50 rand, the formula becomes:
[tex]\[ \text{Total income} = 50 \times \text{Number of photographs} \][/tex]
#### 1.3 The total expenses can be calculated using the following formula:
[tex]\[ \text{Expenses (in rand)} = 1125 + (\text{number of photographs} \times 5) \][/tex]
##### (a) Write down the variable cost for taking ONE photograph.
From the given formula:
[tex]\[ \text{Expenses (in rand)} = 1125 + (\text{number of photographs} \times 5) \][/tex]
We can see that the variable cost for taking one photograph is the coefficient of the number of photographs term in the expense formula, which is:
[tex]\[ \text{Variable cost per photograph} = 5 \text{ rand} \][/tex]
So, the variable cost for taking one photograph is 5 rand.
##### (b) Calculate the missing value [tex]\( A \)[/tex].
To calculate the missing value [tex]\( A \)[/tex] for 80 photographs using the expense formula given:
[tex]\[ \text{Expenses} = 1125 + (\text{number of photographs} \times 5) \][/tex]
Here, the number of photographs is 80, so:
[tex]\[ A = 1125 + (80 \times 5) \][/tex]
[tex]\[ A = 1125 + 400 \][/tex]
[tex]\[ A = 1525 \][/tex]
So, the missing value [tex]\( A \)[/tex] is 1525 rand.
Let's summarize the answers:
1.1. The selling price of one photograph is 50 rand.
1.2. The formula for calculating total income is [tex]\( \text{Total income} = 50 \times \text{Number of photographs} \)[/tex].
1.3.
(a) The variable cost for taking one photograph is 5 rand.
(b) The missing value [tex]\( A \)[/tex] is 1525 rand.
