He has used the purchasing power parity formula from the formula sheet.
The relevant spot rate now is 175; the rates of inflation are 5% in the home country and 30% in the foreign country. So the forecast spot rate in 1 years time is 175 x (1.30/1.05) = 217 Similarly in 2 years time it will be 217 x (1.30/1.05) = 269
For the rate in 6 months time he has taken half way between the current spot and the rate in 1 years time. For the rate in 18 months time he has taken half way between the 1 year and 2 year forecasts.