Question 1204486
The illumination can be written as

I = k cp /d^2

I illumination
cp power of lamp
distance of object from lamp

I = k*cp/d^2


k*8/150^2= k*5/d^2

8 d^2 = 5*150^2

d^2 = (5/8)150^2

d = 150 sqrt(5/8)

d = 118.5cm

lower it 150-118.5 = 31.5 cm

The lamp has to be lowered by approx 31.37 cm to provide the same illumination as before.