help

We can write two equations for this...

Where d=number of dimes and n=number of nickels.. In cents the equation will be:

10d+5n=210

d+n=30

We can use the elimination method to get

10d+5n=210

10d+10n=300

Then subtract.

-5n=-90.

So the number of nickels is 18.

That makes the number of dimes 12.

In total, he has 210 cents

n + d = 30

5n + 10d = 210

multiply 5 to the first equation

then minus the first from the second one

you get 60 = 5d

12 dimes or 12 y

and 

18 nickels or 18 x

Thanks, brian  and CTG    !!!!