What would the following code do : X = Y = 7 ?

What is the error in following code : X, Y = 7 ?

"Comments are useful and easy way to enhance readability and understandability of a program." Elaborate with examples.

From the following, find out which assignment statement will produce an error. State reason(s) too.

(a) x = 55
(b) y = 037
(c) z = 0o98
(d) 56thnumber = 3300
(e) length = 450.17
(f) !Taylor = 'Instant'
(g) this variable = 87.E02
(h) float = .17E - 03
(i) FLOAT = 0.17E - 03