Answer:
constant of proportionality will be 6
Explanation:
In the given graph number of meal prepared and number of days have been graphed
Since relation between them has been represented by a straight line, so their relation can be represented by 
Number of meals prepared × number of days
or Number of meals = K × number of days
where K is the proportionality constant.
Now K = 

 = 

 = 6
therefore, constant of proportionality will be 6