First of all, you can move the +2x to the other side:
-11 = -26 - 2x
Then you can move the -26 to the other side and then simplify:
-11+26 = -2x
15 = -2x
Then you can divide both sides by 2:
7.5 = -x
Then you can flip the sides and the signs around:
x = -7.5
No, The answer is not -7, it is -7.5
Hope this helps! :)
The formula can be written in the form ...
... T = (original temperature) + x·(change in temperature each minute)
The problem statement gives you the original temperature (21 °C) and tells you the temperature after 12 minutes. You have to use that information to figure out the change in temperature each minute.
The change in temperature in 12 minutes is (75 °C) - (21 °C) = 54 °C. That is the change in 12 minutes, so the change in 1 minute will be 1/12 of that:
... 54/12 = 4.5
Using this value in the equation for T, we have
... T = 21 + 4.5x
