Answer:
15 inches
Step-by-step explanation:
We have that,
Length of the photo = 4 inches and Width of the photo = 6 inches
Also, the width of the image on the calendar = 10 inches
Let, the length on the image of the calendar = x inches.
Since, the ratio of the photo and its image will remain same, we get,

i.e. 
i.e. x = 15
Hence, the length of the image of the photo on the calendar is 15 inches.
The slope is 2, as for every 20 the graph rises, the line goes over 10, and the formula for slope is rise over run.
Well i believe its 23 my son