Acceleration = (change in speed) / (time for the change)
= (76.8 mi/hr) / (7.62 sec)
= 10.08 mile/hour-second
That quantity is a perfectly good acceleration, it has the right
dimensions etc, but the question asks for it in units of meter/s²,
so I have to convert it to the equivalent in meter/s².
(10.8 mile / hr-sec) x (1,609 meter/mile) x (1 hr / 3600 sec)
= (10.8 · 1,609 · 1) / (3,600) meter / second²
= 4.83 meter / second² if you round all the numbers as you go
or
4.51 meter/sec² if you use a calculator and don't round anything