Answer:400 yards
Step-by-step explanation:Let L represents the position of library, R represents the restaurant and M represents the museum,
Since, By the given diagram,
∠MLR = 90°,
LR = 300 yd,
RM = 500 yd,
So, by the Pythagoras theorem,
By substituting the values,
Hence, the distance between library and museum is 400 yards.