Describe an experiment in which the resultant of two forces directed along one straight

Describe an experiment in which the resultant of two forces directed along one straight line in one direction is determined. What is this resultant equal to?

We have a spring and two weights of 1 and 2N. Hanging them on the spring, we mark how long it has stretched. Then we take one weight with the weight of ZN, and we will see that the spring is stretched to the same length. From this experience it follows that the resultant of these forces, directed along one straight line in one direction, is directed in the same direction, and its modulus is equal to the sum of the moduli of the constituent forces. Analytically it will look like this: R = F1 + F2