Answer:
Q=7200 W
q=7200/72=100

Step-by-step explanation:
Given that
ΔT=15° C
Thickness ,t=15 cm
Thermal conductivity ,K=1 W/m.°C
Height,h=6 m
Length ,L=12 m
As we know that heat conduction through wall given as

Now by putting the values
A= 6 x 12 =72



Q=7200 W
Q is the total heat transfer.
Heat flux q
q=Q/A

q=7200/72=100

q is the heat flux.
As w know that heat flux(q) is the heat transfer rate from per unit area and on the other hand heat transfer(Q) is the total heat transfer from the surface.
Heat flux q=Q/A
That is why these both are different.