Let’s use Newton’s Laws of Motion to determine a few things…

First the of the car:

##a = (v_f – v_i)/t## where ##v_f = 26.82 m/s; v_i = 0; t = 8.0 s##

##a = (26.82 – 0)/8.0 = 3.35 m/s^2##

Now to determine the final speed when ##v_i = 22.35 m/s; t = 5 s; a = 3.35 m/s^2##

##v_f = v_i + at##

##v_f = 22.35 + 3.35*5 = 39.1m/s##

The same problem in English units of miles per hour:

Acceleration of the car from 0mi/h to 60mi/h in 8.0s:

##a = (v_f – v_i)/t## where ##v_f = 60mi/h; v_i = 0; t = 8.0 s##

##a = (60mi/h – 0)/8.0s = 7.5mi/h/s##

Final speed when initial velocity is 50mi/h:

##v_i = 50mi/h##; ##a = 7.5mi/h/s##; ##t = 5.0s##

##v_f = v_i + at##

##v_f = 50mi/h## + (##7.5mi/h/s##)(##5.0s##)

##v_f = 50mi/h + 37.5mi/h = 87.5mi/h##