Question 586620
Where D is the speed in km/h that Dale drives at,
2D+2(D+2)=68

Divide both sides by 2:
D+(D+2)=34km, or 2D+2=34

Subtract 2 from each side:
2D=32

Divide both sides by 2:
D=16

Now, since Dale drives at 16km/h, and Laura drives 2km/h faster, Laura drives at 18km/h.

In two hours, Dale dove 32km, and Laura drove 36km, for a combined total of 68km.