Answer:
Explanation:
We need to find the unit value, so divide 9 by 15.
9 / 15 = $0.60
Since one baseball card costs 60 cents, we multiply by 30 to find the cost of 30 baseball cards.
$0.60 * 30 = $18.00
30 baseball cards cost $18.00
ALTERNATE SOLUTION:
Since 15 is half of 30, just multiply $9.00 by two to get your answer of $18.00