Question 661215
(FLIGHT CONDITIONS) In stable air, the air temperature drops about 5 °(F) for each 1,000-foot rise in altitude. 
(A) If the temperature at sea level is 100 °F and a commercial pilot reports a temperature of -30 °F at 26000 feet, write a linear equation that expresses temperature T in terms of altitude A.
**
linear equation takes the form: y=mx+b, m=slope, b=y-intercept
For given problem:
slope=-5º/1000 ft
equation: 
T=-5A/1000+b
using coordinates (26000 ft,-30º) of given condition to solve for b
-30=-5*26000/1000+b
-30=-130+b
b=100
equation:
T=-5A/1000+100