Final answer:
The means in the given proportion a/10 = b/3 are '10' and '3'.
Step-by-step explanation:
In the proportion a/10 = b/3, the means refer to the values between the extremes.
In this case, the means are represented by '10' and '3'. So, '10' is the mean for the first ratio a/10, and '3' is the mean for the second ratio b/3.