Sasha has some pennies, nickels, and dimes in her pocket. The number of coins is 16. The expression 0.01p+0.05n+0.10d represents the value of the coins, which is $1.22. She has twice as many nickles as pennies. How many of each coin does Sasha have?

I would like to use cents

p+n+d=16

1p+5n+10d=122

twice as many nicklese a pennies, n=2p

sub 2p for n

p+2p+d=16

1p+5 (2p) + 10d=122

simplified

3p+d=16

1p+10p+10d=122

3p+d=16

11p+10d=122

now solve

use subsitution

3p+d=16

minus 3p from both sides

d=16-3p

sub 16-3p for d in other equation

11p+10 (16-3p) = 122

11p+160-30p=122

160-19p=122

minus 160 both sides

-19p=-38

divide both sides by - 19

p=2

sub back

n=2p

n=2 (2)

n=4

d=16-3p

d=16-3 (2)

d=16-6

d=10

2 pennies

4 nickles

10 dimes