If general equation of hyperbola is
then we can calculate linear eccentricity `e>0` by using formula
and then the foci are `F_1(-e,0)` and `F_2(e,0)`.
Let's now apply that to your case. Here we have `a^2=64` and `b^2=36` hence
So the foci are `F_1(-10,0)` and `F_2(10,0).`