Answer:
99
Explanation:
15x9=135
135 cm
18x13=234
234 cm
234-135=99
=99
Area = 99cm^2
Seen cardboard = Total cardboard - picture
Total cardboard = 18 * 13
Total cardboard = 234
Picture = 15 * 9
Picture = 135
Seen cardboard = 234 - 135
Seen cardboard = 99
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