Add another defer exercise

exercises/116_defer3.zig

@@ -0,0 +1,18 @@
+//
+// When there are multiple defers in a single block, they are executed in reverse order.
+//
+const std = @import("std");
+
+pub fn main() void {
+    var x: u32 = 100;
+    {
+        // Try reordering the statements to get the answer 42
+        defer x = x / 10;
+        defer x = x + 11;
+        defer x = x * 2;
+
+        // It might seem silly in this example, but it's important to know when
+        // deinitializing containers whose elements need to be deinitialized first.
+    }
+    std.debug.print("{d}\n", .{x});
+}