Acar moving at 4.5 m/s accelerates at 2.5 m/s2 (the two is squared) after 7s, it will be moving how fast?

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.

The answer is b hope this