switching last two hex questions (#533)

So a trainee has to convert the hex into a number before considering how
this might look as colours.

Ideally to improve lead into the idea of that % of bytes used can create
the colour mix.

Same could be said for the grey question needing more suggestion of how
to calculate a colour mix (somehow hinting or leading to the idea of
proportion of bytes used).

Suggestions welcome for whether this fixes a misunderstanding or not, or
if it can be improved.

Author: Poonam-raj

number-systems/Part-2.md

@@ -7,16 +7,16 @@ The goal of these exercises is for you to gain an intuition for binary numbers.
 The answers to these questions will require a bit of explanation, not just a simple answer.
 
 Q16: How can you test if a binary number is a power of two (e.g. 1, 2, 4, 8, 16, ...)?
-Answer: 
+Answer:
 
 Q17: If reading the byte 0x21 as an ASCII character, what character would it mean?
-Answer: 
+Answer:
 
 Q18: If reading the byte 0x21 as a greyscale colour, as described in "Approaches for Representing Colors and Images", what colour would it mean?
-Answer: 
+Answer:
 
-Q19: If reading the bytes 0xAA00FF as an RGB colour, as described in "Approaches for Representing Colors and Images", what colour would it mean?
-Answer: 
+Q19: If reading the bytes 0xAA00FF as a sequence of three one-byte decimal numbers, what decimal numbers would they be?
+Answer:
 
-Q20: If reading the bytes 0xAA00FF as a sequence of three one-byte decimal numbers, what decimal numbers would they be?
-Answer: 
+Q20: If reading the bytes 0xAA00FF as an RGB colour, as described in "Approaches for Representing Colors and Images", what colour would it mean?
+Answer: