Question

PQRS is a parallelogram.if ST=8cm,PQ=4cm and RQ=6cm find QU.

Answer 1

area=PQ*ST
=8*4
=32
also 
area = RQ*QU
 32=6*QU
QU=32/6
        =5.3 cm

Answer 2

See the figure for the reference
ST = 8 cm
PQ = 4 cm
 area of PQRS = base x height 
                      = PQ x ST
                      = 8 x 4 
                      =32 cm²

we can also say that 
base of PQRS is RQ
height of PQRS is QU

area of PQRS = RQ x QU
               32 = 6 x QU
            32/6 = QU
            5.33 cm = QU