Moved exercises to exercises because exercises

exercises/10_if2.zig

@@ -0,0 +1,25 @@
+//
+// If statements are also valid expressions:
+//
+//     var foo: u8 = if (a) 2 else 3;
+//
+// Note: You'll need to declare a variable type when assigning a value
+// from a statement like this because the compiler isn't smart enough
+// to infer the type for you.
+//
+// This WON'T work:
+//
+//     var foo = if (a) 2 else 3; // error!
+//
+const std = @import("std");
+
+pub fn main() void {
+    var discount = true;
+
+    // Please use an if...else expression to set "price".
+    // If discount is true, the price should be $17, otherwise $20:
+    var price = if ???;
+
+    std.debug.print("With the discount, the price is ${}.\n", .{price});
+}
+