Answer:
5ax - 14by + 15
Step-by-step explanation:
The calculation required is
9ax - 6by + 8 - (4ax + 8by - 7 ) ← distribute parenthesis by - 1
= 9ax - 6by + 8 - 4ax - 8by + 7 ← collect like terms
= (9ax - 4ax) + (- 6by - 8by) + (8 + 7)
= 5ax + (- 14by) + 15
= 5ax - 14by + 15
