I really need help on this one, guys

Answer:
6.2 meters
Step-by-step explanation:
Use pythagorean theorem to find b:
b = √(2.8² - 2.7²) = √0.55 = 0.7 (nearest tenth)
Perimeter of triangle = sum of all its sides = 2.8 + 2.7 + 0.7
Perimeter = 6.2 meters