Question 697857
This looks like a linear relation between milage, {{{ m }}}
and speed. They give you a point, ( s[1] , 7 )
if you plot milage on the vertical axis and miles driven
on the horizontal axis. They are also giving you the
slope of the line. Slope = {{{ -.1 / 1 }}}
But you didn't give me a speed, {{{ s[1] }}} when the milage
is {{{ 7 }}} miles/gallon.
If {{{ s[1] }}} is given, I can set up a point-slope formula:
{{{ ( m - 7 ) / ( s - s[1] ) = -.1/1 }}}
This would give you the equation
{{{ m - 7 = (-1/10)*( s - s[1] ) }}}
{{{ 10m - 7 = -s + s[1] }}}
{{{ 10m = -s + s[1] + 7 }}}
{{{ m = (-1/10)*s + ( s[1] + 7 ) / 10 ) }}}
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Like I said, you need {{{ s[1] }}}, the speed at which 
the milage is {{{ 7 }}} mi/gal