Kurt enlarges a 24 cm by 30 cm photo to a 60 cm by 75 cm photo. what is the scale factor of the enlargement?

One scale factor equation is y=cx
y is the new factor    (in this case, 60 or 75)
c is the scale factor   (in this case, unknown)
x is the old factor      (in this case, 24 or 30)
so:   plug in the values
60=c(24)         divide both sides by 24
c=2.5

you can check again with the other numbers
75=c(30)           divide both sides by 30.
c= 2.5

your scale factor is 2.5