(a) Since true bearings are measured clockwise from 0° from the north line, the south line is 180°.
S48°W is 48° from the South line to the West line and goes clockwise so the true bearing is
180° + 48° = 228°
Reverse the procedure for (b). 335° is 25° away from the north line (360° - 335° = 25°) so it's N25°W