Explanation
From the question, we can see that the triangle is a right angled triangle. Hence, it obeys the law of Pythagoras, which is the Pythagorean theorem.
This formula is defined as:
It states that the length of the square of the hypotenuse(longest side) is equal to the sum of the squares on the other two sides.
This implies that;
[tex]\begin{gathered} 13^2=11^2+x^2 \\ x^2=13^2-11^2 \\ x^2=169-121 \\ x^2=48 \\ x=\sqrt[]{48} \\ x=6.9 \end{gathered}[/tex]
Answer: 6.9
