Question 1071363
<pre>
            SPEED   TIME      DISTANCE
Part1        5       x           5x
Part2        10      y           10y
Total              x+y           35
AVERAGE      7
</pre>


Average speed is total distance divided by total time.


{{{system(35/(x+y)=7,5x+10y=35)}}}


Note that total time can be found just from the average speed, the first equation.


{{{x+y=35/7}}}

{{{x+y=5}}}------ 5 hours total time.


-
{{{5x+10y=35}}}
{{{x+2y=7}}}


Revised system:
{{{system(x+2y=7,x+y=5)}}}


{{{highlight(y=2)}}}
-
{{{highlight(x=3)}}}