Answer:
x = 4.4 cm
Step-by-step explanation:
Since this is a right triangle, the Pythagorean Theorem applies: a^2 + b^2 = c^2, where a and b are leg lengths and c is the length of the hypotenuse.
Thus, (5.3 m)^2 + x^2 = (6.9 m)^2, or, solving for x^2:
x^2 = (6.9 m)^2 - (5.3 m)^2, or
x^2 = 47.61 - 28.09 = 19.52
Then the length, x, of the unknown side is x = +√19.52 m, or
x = 4.4 cm
