a + b   = (4, 6)
b - a   = (2, 2)
a * 3   = (3, 6)
-a      = (-1, -2)
a == a  = true
a == b  = false
a < b   = true
b > a   = true
a[0]    = 1
a[1]    = 2
a now   = (10, 2)
