A body covers 80 meter in 7th second,124 meter in 9th second, how much shall it covers in 15 second?

d(8)-d(7)=vo*8-vo*7 +1/2 a *64-1/2 a*49=vo+1/2 a*15=

equation 1: 80=vo+7.5a

do the same meth for the 15second (distance 16-distance 15), then get and eequation 2.

You have two equations, solve for vo, and a.

Finally then you can solve for the distance in the 15th second.