Someone please help me answer this!!

Answer:
a = 15yd is the answer.
Step-by-step explanation:
a = ?
b = 8yd
c = 17yd
By using the Pythagoras theorem,
a² + b² = c²
a² + 8² = 17²
a² + 64 = 289
a² = 289 - 64
a² = 225
a = 15
∴ a = 15yd is the length of the missing leg.