A balloon starts from ground with acceleration of 1.25 metre per second square and after 8 sec a stone is released from it so after how much time stone will reach the ground?

The ballon starts from rest. We make use of the equation

here,
u=0 and a=1.25 m per sec square
So, at the end of 8 seconds,
S= 40 metres
So, now a stone is released from initial velocity zero
again we use the same equation, where we know that s= 40 m
now the acceleration will be due to gravity we take it as a= 10 m per sec square
and u= 0
So, we get t= 2.83 seconds approximatly.