For 8pq-3pq:
The variables are the same, so all you have to do for this one is subtract the numbers
8pq-3pq: 5pq
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For 2m-3m+4:
The like terms in this equation are the ones with the same variable. This would be 2m and 3m, which turns into -1m or simply -m.
2m-3m+4: -1m+4