Let

v = average speed

d = distance travelled

t = the time of the trip

We know that

v = d/t

Solving for 't' we have:

t = d/v

Mr Dunn drives 64.8km from work at a speed of 48km/h means:

d = 64.8 km

v = 48 km/h

t = d/v

t = 64.8/48

t = 1.35 hr

t = 1 hr 21 min

Mrs Dunn drives 81.2km from work at a speed of 58km/h means:

d = 81.2 km

v = 58 km/h

t = d/v

t = 81.2/58

t = 1.4 hr

t = 1 hr 24 min

a) Who arrives home first?

Mr Dunn arrives home first since 1 hr 21 min is less than 1 hr 24 min.

b) How many minutes later is it before the second person gets home?

1 hr 24 min - 1 hr 21 min = 3 min

The second person, Mrs Dunn, gets home 3 minutes later.