Hello, Bianca,
I might not understand the question entirely, but it would appear that Jim has travelled 3 kilometers (3 km) plus 100 meters (100 m). The problem is simply converting one of the units of km or m to the other, so that they can be added.
Since 1 km = 1000 meters, we can make this into a conversion factor. Since the question does not specify what unit is desired (km or m), we could chose either one. If we want km, the 100 m must be converted into km. I'll choose km, so show how it's done.
We'll need to covert the 100 m into km, so lets arrange 1 km = 1000 m by dividing by 1000 m.
This gives us (1 km/1000 m) = 1
Since this expression is equal to 1, it becomes a conversion factor. We can multiply 1 times anything, and it doesn't change the result EXCEPT for the units. To convert 100 m into km:
(100m)*(1km)/(1000m) = 0.10 km (note how the meters cancel out)
Now we can add 1km + 0.1km to find total distance Jim travelled, which is 1.1km.
If Jim want a more impressive number to impress the girls, he could choose to calculate the distance in meters, instead of km. Just use the inverse of the conversion factor (it is still equal to 1!).
(1km)(1000m/1km) = 1000m
Total distance = 1100 meters. Several girls were impressed, but not Jean, who asked "Wait. How many feet is that? 1000 meters is only 1.1 km. Big deal."
To determine feet, use a conversion factor. 1 meter = 3.28 feet.
I'll divide by the 1 meter: 1 = (3.28 feet)/(1 meter).
I divided by the meter to put meter on the bottom, so that I can multiply it directly against the 1000 meters and the meters cancel, leaving just feet. You can do it the other way with 1m/3.28ft, but I hate division. Since either way is correct, take your pick. That's the wonderful thing about conversion factors: you can always invert them to put them into the format that makes you happiest.
I hope this entertains, and helps,
Bob
