Answer:
11.2cm
Step-by-step explanation:
To be able to determine the missing length, we have to apply the Pythagorean Theorem which states that, in a right-angled triangle, the square of the hypotenuse(the longest side) is equal to the sum of squares of the other two sides.
Let's go ahead and find b as follows;
![\begin{gathered} 14^2=8.4^2+b^2 \\ 196=70.56+b^2 \\ 196-70.56=b^2 \\ 125.44=b^2 \\ b=\sqrt[]{125.44}=11.2\operatorname{cm} \end{gathered}]()