Using ruler and a pair of compasses only,
(a) construct (i) a quadrilateral PQRS with /PS/ = 6 cm, < RSP = 9 cm, /QR/ = 8.4 cm and /PQ/ = 5.4 cm; (ii) the bisectors of < RSP and < SPQ to meet at X ; (iii) the perpendicular XT to meet PS at T.
(b) Measure /XT/.
Explanation
(a) 
(b) /XT/ = 3.4 cm.