You shouldn't have anything as complicated in the NATS test but I would work it out like this.
223mph / 2 = 111.5 miles in 30mins.
111.5/10 = 11.15 miles in 3 minutes.
111.5 - 11.15 = 100.35 miles in 27minutes.
A lot easier to break it up into chunks when you don't have a calculator.