i do not know this answer, i need help

Answer:
18 kilometers
Step-by-step explanation:
if you know the perimeter, then all you have to do is add up what you have, 10+7=17 and then subtract it giving you the bits that you dont know, so 35-17=18 kilometers.
Answer:
s = 9 Km
Step-by-step explanation:
the perimeter is the sum of the 4 sides
given perimeter = 35 , then
10 + 7 + s + s = 35
17 + 2s = 35 ( subtract 17 from both sides )
2s = 18 ( divide both sides by 2 )
s = 9 Km