Write down the formula to calculate the cost of a single trip, where x will represent the number of hours travelled and y represent the cost of the trip.

The bus company charges a flat rate of $\text{R}50$. This is the fixed cost.
The bus company charges $\text{R}30$ for every hour of the trip per person. This is the variable cost per hour.

Let $x$ represent the number of hours traveled and $y$ represent the cost of the trip.
The total cost $y$ is the sum of the flat rate and the hourly rate multiplied by the number of hours.

The formula to calculate the cost of a single trip is $\boxed{y = 30x + 50}$.

• For $x = 0$ hours: $y = 30(0) + 50 = 0 + 50 = 50$
• For $x = 1$ hour: $y = 30(1) + 50 = 30 + 50 = 80$
• For $x = 2$ hours: $y = 30(2) + 50 = 60 + 50 = 110$
• For $x = 3$ hours: $y = 30(3) + 50 = 90 + 50 = 140$

Here is the completed table: