algebra help please - with $63 total, if there were 4 times as many dimes as nickles, how many of each coin?

My mother is taking an algebra class. I'm trying to help her. I used to be good with algebra. I used some math and plotted through different answers, so I know the answer is nickels=140 and dimes=560.

But I'm going wrong when I try to figure it out.

This is what I have.. tell me what I'm doing wrong?

I converted 63 bucks into cents only so that I work with whole number and not decimals (I hate decimals.)

so attempt #1:

6300=4n+n (where n=nickels)

then I put in the values of the cents

6300=4n(10)+n(5)

6300=40n+5n

6300=45n

n=144.4444444?????

that can't be right. I'm sure I was suppose to get a whole number?! Right?!

Okay, attempt #2 (with decimals):

63.00=(0.10)4n+(0.05)n

63=0.4n+0.5n

63=0.9n

n=70

I know that's not right either. Because 4 times that would be 280dimes with is 28.00

70 nickels=a few bucks... this doesn't total 63 bucks.

Help?