The formula is
V = final velocity = initial velocity U + ( acceleration a * time duration t )
V = U + a t
= 4.5 m/s + 2.5 m/sec² * 7 sec = 4.5 + 17.5 = 22 m /sec
Acceleration means, every second the velocity or speed increases by that amount. Here it is 2.5. After one second velocity become 2.5 m/s more. after 2 seconds it is 5 m/s more. after 3 seconds, speed is 7.5 m/s more than at start. Like this after 7 seconds, the speed is 7 * 2.5 higher than at the beginning. so computer the total.
