Use the Pythagorean theorem
Side = sqrt(8^2 - 6^2)
Side = sqrt(64-36)
Side = sqrt(28)
Side = 5.29
Rounded to nearest tenth = 5.3
Given equation of hyperbola is

Given hyperbola is the horizontal hyperbola
The standard form of the horizontal hyperbola is

When we compare these two equations, we get
h = 1, a = 5 , k = -3 and b = 3
Length of the transverse axis = 2a
Plug in the value of 'a' as 5
So,Length of the transverse axis = 2(5) = 10