Consistent instructions and examples

I started off with "hints" that required the poor student to piece
together the information from incomplete bits. A complete example is
like a picture that is worth 1000 words and far clearer.

09_if.zig

@@ -1,19 +1,19 @@
 //
 // Now we get into the fun stuff, starting with the 'if' statement!
 //
-//   if (true) {
-//      // stuff
-//   } else {
-//      // other stuff
-//   }
+//     if (true) {
+//         ...
+//     } else {
+//         ...
+//     }
 //
-// Zig has the usual comparison operators such as:
+// Zig has the "usual" comparison operators such as:
 //
-//   a == b   a equals b
-//   a < b    a is less than b
-//   a !=b    a does not equal b
+//     a == b   means "a equals b"
+//     a < b    means "a is less than b"
+//     a !=b    means "a does not equal b"
 //
-// The important thing about Zig's 'if' is that it *only* accepts
+// The important thing about Zig's "if" is that it *only* accepts
 // boolean values. It won't coerce numbers or other types of data
 // to true and false.
 //
@@ -22,6 +22,7 @@ const std = @import("std");
 pub fn main() void {
     const foo = 1;
 
+    // Please fix this condition:
     if (foo) {
         // We want out program to print this message!
         std.debug.print("Foo is 1!\n", .{});