Answer
Each marble adds 0.3cm to the level of the water.
This is found by applying the rate of change which is 0.3 to the problem at hand. The rate of change describes how the dependent value (water level) changes with an increase of the independent value (number of marbles). The formula $ \frac{7.5-6.9}{5-3} $ gives us this value of 0.3. Keeping this in mind, it is clear that the water level is changing by 0.3cm with each marble that is added to the water.
Work Step by Step
Explanation above.
