15m and 24cm is 15.24m
because there's 100cm in 1m so 24cm/100cm = 0.24m
If for some reason you do need 2cm and 98cm, that's 1m so 16.24m
Now, I believe you meant to say 2m instead of 2cm for her friend's garden because it says cm twice.
If that's the case,
2m + 98cm = 2.98m
2.98m + 15.24m = 18.22m
