ex10 - missing type was confusing and tangential (#12)

exercises/10_if2.zig

@@ -10,7 +10,7 @@ pub fn main() void {
 
     // Please use an if...else expression to set "price".
     // If discount is true, the price should be $17, otherwise $20:
-    var price = if ???;
+    var price: u8 = if ???;
 
     std.debug.print("With the discount, the price is ${}.\n", .{price});
 }