Answer:
40km
Explanation:
Average speed can be computed with the equation:
[tex]\bar{s} = \dfrac{total\;distance\;traveled}{Total\;time\;traveling}[/tex]
So we know the average speed and one of the distances is already given and we need to know how much it traveled after that. The total time the car traveling is 2 hours. Let's plug that in our equation:
[tex]\dfrac{70km}{hr} = \dfrac{100km + x}{2hours}[/tex]
Now let's multiply both sides by 2 hours:
[tex]\dfrac{70km(2hr)}{hr} = 100km + x[/tex]
Cancel out the hours and multiply:
[tex]70km(2) = 100km + x[/tex]
[tex]140km = 100km + x[/tex]
Subtract 100km from both sides of the equation:
[tex]140km - 100km= 100km - 100km + x\\\\40km = x[/tex]
