Answer:
![t(x) = 103 -0.0045x](https://img.qammunity.org/2021/formulas/mathematics/high-school/bc70gw4gv3l41s0xnbvk4ftfp0v7jp6tu4.png)
Explanation:
We are given the following in the question:
Let the equation:
![t(x) = a + bx](https://img.qammunity.org/2021/formulas/mathematics/high-school/y9w9db4oikmj16wqsks9fl3pzztga1nyu0.png)
be the linear equation that represent temperature at an elevation x.
Temperature at 6000-foot level = 76 f
![76 = a + 6000b](https://img.qammunity.org/2021/formulas/mathematics/high-school/w4hvhvc0ec7vr3puq6ib7qzrjr723xj99e.png)
Temperature at 12000-foot level = 49 f
![49 = a + 12000b](https://img.qammunity.org/2021/formulas/mathematics/high-school/q68xbzlvw2ntw24fa62xft7el64gd3zauv.png)
Solving the two equation, we get,
![76-49 = -6000b\\27=-6000b\\\\b = (-27)/(6000)\\\\b = -0.0045\\76 = a + (-0.0045)6000\\76 = a -27\\a = 76 + 27\\a =103](https://img.qammunity.org/2021/formulas/mathematics/high-school/n6u3ej3pox8pjkddws2u6w6ohk7gs8refu.png)
Thus, we can write the linear equation as:
![t(x) = 103 -0.0045x](https://img.qammunity.org/2021/formulas/mathematics/high-school/bc70gw4gv3l41s0xnbvk4ftfp0v7jp6tu4.png)