dijawab dengan pakai cara

Luas Δ = (a x t) /2

Luas PQR = (RQ x PM) /2
Luas PQR  = (PQ x RL)/2
Luas PQR = (PR x KL)/2
..
RQ x PM = PQ x RL = PR x KL
.
RQ x PM = PQ x RL
18 x 10 = PQ x 12
PQ = 180./12 = 15

RQ x PM = PR x  KL
18 x  10 = PR x 15
PR  = 180/15 = 12

Keliling PQR = RQ + PQ + PR
K = 18 + 15 + 12
K = 45