Question 1186842
<pre>
{{{drawing(400,10000/37,-3.9,10.9,-3,7,
locate(-1,-.2,matrix(2,1,RADAR,ANTENNA) ),locate(8.1,6.2,AIRPLANE),
line(-3,6,8,6), line(0,0,0,6), line(0,0,8,6),locate(-.5,3,6),
locate(3.5,6.7,x),locate(4,3,s) )}}}

First, we treat x and s as variables:

{{{matrix(4,5,
s^2,""="",x^2,""+"",6^2,
s^2,""="",x^2,""+"",36,
2s*expr(ds/dt), ""="",2x*expr(dx/dt),"","",
s*expr(ds/dt), ""="",x*expr(dx/dt),"","")}}}

Now we freeze the variables when s=10, and we use the
value of x when s=10

{{{matrix(5,5,
s^2,""="",x^2,""+"",36,
10^2,""="",x^2,""+"",36,
100,""="",x^2,""+"",36,
64,""="",x^2,"","",
8,""="",x,"","")}}}

Now we substitute s=10, x=8, and {{{ds/dt=230}}}

{{{matrix(4,3,
s*expr(ds/dt), ""="",x*expr(dx/dt),
10*(230),""="",8expr(dx/dt),
2300,""="",8expr(dx/dt),
287.5,""="",dx/dt)}}}

The speed of the airplane is 287.5 mph.

Edwin</pre>