To determine the extremes in a proportion, we start by recalling that a proportion can be written in the form \( \frac{a}{b} = \frac{c}{d} \). In this form, \( a \) and \( d \) are referred to as the extremes, while \( b \) and \( c \) are the means.
Given the proportion \( \frac{3}{15} = \frac{12}{60} \), we identify the following elements:
- \( a = 3 \)
- \( b = 15 \)
- \( c = 12 \)
- \( d = 60 \)
According to the definition:
- \( a = 3 \) (an extreme)
- \( d = 60 \) (an extreme)
Therefore, the extremes of the proportion \( \frac{3}{15} = \frac{12}{60} \) are \( 3 \) and \( 60 \).
So, the best answer is:
C. 3 and 60
