Is "Forward Voltage @ 1A" equivalent to "Internal Voltage Drop"
Tjhere is not enough information here to make a unique decision.
If the course is designed to help you learn to 'think on your feet' - plough on :-).
If there is meant to be one correct answer, ask for / demand more data.  

Similar to what Majenko says, this sounds like a 12V supply targeted LED string BUT without specific or additional advice this is only a conjecture.

I'd have "guessed" 3 LEDs with 9.5V / 3 = 3.166V/LED ~= 3.2V /LED.
~= 3.2V is typical for white LEDs.
Majenko's 5 x 1.9V might be red LEDs.
In either case the voltage drop is an approximation, as LED Vf will vary with current, and current varies with applied voltage, and voltage ... . 

As per Majenko's result, Iled expected nominal
I = V/R = (12-9.5) / 15.1 ~= 166 mA.

If this string was used in an automotive application where Vsupply can be eg 14V then if Vled did not vary (but, it would) then Istring 
= V/R = (14-9.5)/15.1 = 530 mA or 3+ times as high as at 12V supply!

In practice VLED will rise as ILED rises, serving to somewhat reduce current rise.
eg if VLED = 3.5V/LED at higher current then at 14V
Istring = (14 - 3 x 3.5) / 15.1 ~= 230 mA.
While less than the above 530 mA, this is still ~= 50% higher than at 12V supply.  

A good illustration of why LEDs should be current driven where possible.
A higher series R (and Ferber LEDs to compensate) will have less current variation with voltage, as the higher series resistance more closely approximates a current source.