Answer is 5a + 6b + 7
16 + 8a - 3a +6b -9 subtract 3a from 8a which is 5a
16 + 5a + 6b -9 Now subtract 9 from 16
7 +5a +6b Now reorder them by the first letter in the alphabet and then regular numbers last.
5a + 6b + 7
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