Fixing Typos: 6-15, 6-18 and 6-19

Author: mrmmarsh

pages/6-15-constant-width.md

@@ -25,10 +25,10 @@ Watch this video where Steve Mould shows an array of shapes with a peculiar prop
 ::: problem id=1_1 marks=2
 __1.1__ Which of these shapes is a solid of constant width?  
 
-* [ ] hexagon
-* [x] circle
-* [ ] triangle
-* [ ] square
+* [ ] Hexagon
+* [x] Circle
+* [ ] Triangle
+* [ ] Square
 :::
 
 ::: problem id=1_2 marks=2

pages/6-18-algorithmic-enchantment.md

@@ -27,9 +27,9 @@ Watch this video where University of Nottingham Professor Roger Bowley explains:
 ::: problem id=1_1 marks=1
 __1.1__ How would you describe the algorithm to arrive at 6,174?
 
-* [x] put the digits in order highest to lowest, reverse the order, and subtract
-* [ ] put the digits in order lowest to highest, reverse the order, and subtract
-* [ ] put the digits in order highest to lowest, reverse the order and add
+* [x] Put the digits in order highest to lowest, reverse the order, and subtract
+* [ ] Put the digits in order lowest to highest, reverse the order, and subtract
+* [ ] Put the digits in order highest to lowest, reverse the order, and add
 :::
 
 ::: problem id=1_2 marks=1

pages/6-19-lucky-numbers.md

@@ -90,7 +90,7 @@ The probability of wining a coin toss is `1/2`.
 
 The probability of rolling a 6 on a standard dice is `1/6`.  
 
-So the combined probability of both of these independet events happening is `1/2 x 1/6 = 1/12`.
+So the combined probability of both of these independet events happening is `1/2 × 1/6 = 1/12`.
 :::