Bantu dong kak.... :)

Perhatikan ∆PRS
PR = √(RS^2 - PS^2) = √(6^2 - 3^2) = √(36 - 9) = √27 = 3√3

Perhatikan ∆PQR
PR^2 = RQ^2 + PQ^2 - 2 . RQ . PQ cos Q
(3√3)^2 = 12^2 + 13^2 - 2 . 12 . 13 cos Q
27 = 144 + 169 - 312 cos Q
312 cos Q = 144 + 169 - 27
312 cos Q = 286
Cos Q = 286/312 = 11/12 = sa/mi
=> de = √(12^2 - 11^2) = √(144 - 121) = √23
Sin Q = de/mi = √23/12

Luas ∆PQR = 1/2 . RQ . PQ . sin Q
= 1/2 . 12 . 13 . √23/12
= (13√23)/2