Question 661215
Plot altitude on the horizontal and temp on the vertical
so, {{{ T = f(A) }}}
The slope of the line will be {{{ -5 / 1000 }}} degrees/feet
You are given 2 points on the line,
( 0, 100 ) the sea level temp, and
( 26000, -30 ) 
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slope = {{{ ( -30 - 100 ) / ( 26000 - 0 ) }}}
slope = {{{ -130 / 26000 }}}
slope = {{{- .005 = -5/1000 }}}
This agrees with the given slope
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Using the point-slope formula:
{{{ ( T - 100 ) / ( A - 0 ) = -.005 }}}
{{{ T - 100 = -.005A }}}
{{{ T = -.005A + 100 }}} answer
check:
does it go through (26000, -30) ?
{{{ T = -.005A + 100 }}} 
{{{ -30 = -.005*26000 + 100 }}}  
{{{ -30 = -130 + 100 }}}
{{{ -30 = -30 }}}
OK
Here's the plot with the horizontal axis expressed
in thousands of feet
{{{ graph( 400, 400, -10, 50, -50, 200, -5x + 100 ) }}}