Let's address each part of the problem one by one.

Question 4.15:

We are given a graph and need to answer the following:

a) What is the daily wage if he sells 20 curves?

To solve this, we will first identify the wage corresponding to 20 curves on the graph. The x-axis represents the number of curves, and the y-axis represents the total wage in kroner (kr). We can trace the point on the graph where the number of curves is 20 and find the corresponding wage.

b) Last Thursday, he earned 900 kr. How many curves did he sell that day?

From the graph, we locate the point where the wage is 900 kr and find the number of curves (x-axis value) corresponding to this wage.

c) Find a formula for $K$.

The wage formula can be derived from the linear relationship visible in the graph. We need to calculate the slope and use it to formulate the equation for $K$, where $K$ is the wage and $x$ is the number of curves.

Question 4.16:

We are given the temperature formula for water cooling over time and asked to answer the following:

a) The producer guarantees that the temperature will be at least 65°C after five hours. Check if this is true using the formula.

We are given the formula $T = 78 - 0.90t + 22$, where $T$ is the temperature in °C and $t$ is the time in hours. We can substitute $t = 5$ to check the temperature at that time and see if it is at least 65°C.

b) What is the meaning of the number 22 in the formula?

The number 22 is the constant in the temperature equation. We can interpret its meaning based on the formula structure.

Question 4.17:

We are given the formula for the volume of a cylinder and asked:

a) What happens to the volume if we keep the radius constant and double the height?

The volume of a cylinder is given by $V = \frac{\pi r^2 h}{3}$. If the radius remains constant and we double the height, we can observe how the volume changes by applying this change to the formula.

b) What happens to the volume if we keep the height constant and double the radius?

Similarly, if we keep the height constant and double the radius, we will observe how this affects the volume by applying this change to the formula.

I can solve these questions step by step, starting with the first one, or I can provide a general answer to all. Would you like me to go ahead and start solving these, or do you have any specific question to focus on?