Answer:
-6
Step-by-step explanation:
17-6=11
11-6=5
5-6=-1
-1-6=-7
the answer is 420
280 m
a² + b² = c²
450² + b² = 530²
202,500 + b² = 280,900
280,900 - 202,500 = 78,400
√78,400 = 280