An altitude of a triangle is a line or segment that passes through a vertex of the triangle and is to the line containing the opposite side.

I think best word to insert in the blank is the term "bisecting".

An altitude of a triangle is a line or segment that passes through a vertex of the triangle and is bisecting to the line containing the opposite side.

"Bisect" means to divide into two equal parts which is true for the altitude of a triangle.

a - base

b - exponent

so,

the base is 8the exponent is 3the exponent tells you to multiply 8 together three timesthe expanded form is 8*8*8