In cases like these, you simply have to multiply the choices you have for each step.
In fact, you can choose between 4 different crusts. For each of these crusts you can choose 4 different sauces. This means that there are 
choices at this point. In fact, if we call the crust options 1,2,3,4 and the sauce options A,B,C,D, the 16 possible combinations are
From here, you keep going multiplying the number of options for each step, for a total of
So you have to find the relationship between the pumpkin diameter (y) and the number of weeks passed (x) in a table, lets do it taking into account that the equation modeling such behaviour is:
y = 2x + 6, where x is the number of weeks and plus original 6 cm
x y
week diameter
0 6
1 8
3 12
5 16
10 26
substitute the x and y values in the equation to see how they fit into it
