**Answer:**

From Plato

30e-0.12t less than or equal to M

40e-0.18t less than or equal to M

**Step-by-step explanation:**

It is given that compound A decays at a rate of 12% per week, and compound B decays at a rate of 18% per week. Since the rates represent decay, the r-value is negative. A decay rate of 12% is represented by an r-value of -0.12, and a decay rate of 18% is represented by an r-value of -0.18.

The initial amount of compound A is 30 grams and the initial amount of compound B is 40 grams. Substitute the initial amounts of each compound and their respective decay rates into the system of inequalities.

The following system of inequalities can be used to determine when the remaining mass of the two compounds, M, will be the same, after t weeks.