Question 100404
Let x=number of nickels
Then 30-x=number of dimes

(1) value of the nickels=0.05x
(2) Value of the dimes=0.10(30-x)


Now we are told that (1) +(2)=2.10.  So our equation to solve is:

0.05x+0.10(30-x)=2.10  get rid of parens

0.05x+3-0.10x=2.10  subtract 3 from both sides

0.05x+3-3-0.10x=2.10-3  collect like terms

-0.05x=-0.90  divide both sides by -0.05

x=18---------------------------number of nickels

30-x=30-16=12----------------- number of dimes

CK

0.05*18+0.10*12=2.10
0.9+1.2=2.10
2.10=2.10


Hope this helps---ptaylor