Answer:
Explanation:
7+8=15 8+7=15 15-7=8 15-8=7
9-8=1 8+1=9 9-8=1 1+8=9
17-8=9 9+8=17 8+9=17 17-9=8
15-9=6 6+9=15 9+6=15 15-6=9
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