You have quarters and nickels saved in a piggy bank. there is a total of 3.45 in quarters and nickels and there are 9 more nickels than quarters. how many nickels and quarters in the piggy bank?

Total number of quarters=10

Total number of nickels=19

Step-by-step explanation:

The expression for the total value of money you have is;

Quarters have a value of= $0.25

Nickels have a value of= $0.05

Total value=(value of quarters×number of quarters)+(value of nickels×number of nickels)

where;

Total value=$3.45

Value of a quarter=$0.25

number of quarters=x

Value of a nickel=0.05

number of nickels=y, but y=x+9

replacing;

3.45=(0.25×x)+0.05(x+9)

3.45=0.25 x+0.05 x+0.45

3.45=0.3 x+0.45

0.3 x=3.45-0.45

0.3 x=3

x=3/0.3

x=10

y=x+9=10+9=19

Total number of quarters=10

Total number of nickels=19

Well 0.95 × 40 = 38 so it would be $38 dollars for 40 pens buying separately 
and a dozen is 12, but 12 doesn't fit into 40 properly so we have to buy 48 pens.
12×4=48, 9.95×4=39.8≡$39.80 so that means that buying the pens separately is cheaper.