Answer:
13 yds
18 yds
11 yds
Step-by-step explanation:`
P=S1 + S2 + S3
42 = (S-5) + S + (S-7)
42 = 3S - 12
54 = 3S
18 = S
To check answer add the sides together
(18-5) + 18 + (18-7)
13 + 18 + 11 = 42
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