Let b be the speed of the boat; and c be the speed of the current. Then:
5b-5c=130
5b+5c=220
10b=350
b=35
c=9
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6. yes, it shows a function because you add one to X and it equals Y.
7. it has both
Per cent = per 100 <== ur answer
10d+5n=220
divide both sides by 5
2d+n=44
d=13+n
sub 13+n for d in other equatin
2(13+n)+n=44
26+2n+n=44
26+3n=44
minus 26 both sides
3n=18
divide both sides by 3
n=6
sub back
d=13+n
d=13+6
d=19
19 dimes
6 nickles