Marino has 30 nickels and dimes. she has 12 more nickels than dimes. how many dimes does mariko have?

Let n be the number of nickels and let d be the number of dimes.

We know that there are 30 nickels and dimes.

n + d = 30

We also know that there are 12 more nickels than dimes

d + 12 = n

Substitute this into n+d = 30

(d + 12) + d = 30

2d + 12 = 30

Subtract both sides by 12

2d = 18

Divide both sides by 2

d = 9

Mariko has 9 dimes.

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