The formula of the midpoint of HE:
We have H(0; 0) and E(2a; 2a). Substitute:
Variables are used in algebra and other branches of mathematis.
They are represented by letters. Usually ( but not necesserally) the letters at the end of the alphabet like x,y and z.
4 and 1.5
4x1.5=6
4+1.5=5.5