Convert 7.5min to s. Hence, 7.5min = 450s
I am assuming the initial velocity is zero here and that 18 is the acceleration and not the velocity.
Therefore you use this formula:
acceleration= (vfinal)/t [Note: velocity initial is not included as it is zero, so it would just cancel out]
vfinal= a*t
=18m/s²*450s
= 8100m/s or 8.1*10³m/s if you correct to proper sigdigs.
Hope this helps!
