Question 1071245
<pre>
                      SPEED       TIME         DISTANCE
First part             90           x            90x
Second part            80           y            80y
Totals                              8            690
</pre>


{{{system(x+y=8,90x+80y=690)}}}


{{{x=8-y}}}
-
{{{9x+8y=69}}}
{{{9(8-y)+8y=69}}}
{{{72-9y+8y=69}}}
{{{-y=69-72}}}
{{{y=72-69}}}
{{{highlight(y=3)}}}---------time in hours at 80 km/h


Distance done at 80 km/h ?
{{{80*3=highlight(240)}}}, in kilometers