<h2>
Answer:</h2>
<h3>x = 13 </h3><h2>
Step-by-step explanation:</h2>
<h3>3x+8=2x+21</h3><h3>solve for x3x8-2x+21</h3><h3>x8=21</h3><h3>x=21-8=13</h3><h3>solution is x=13/</h3>
<h2>HOPE IT HELPS!!!</h2>
<h2>PLZ I NEED BRAINLIEST!!</h2>
Using the sinusoidal function, it is found that the temperature will be below 0ºC between May and August.
<h3>
What is a Sinusoidal function?</h3>
- A sinusoidal function is a function that depends on a trigonometric function, having peaks according to the period and amplitude given by this function.
The function for the average monthly temperature, in m months after January, is given by:

Working with elementary angles, we have that:





From this, we have that it becomes negative after March, and positive before September, removing the middle two options.
Now, we have to test for April and May, that is, m = 4 and m = 5, hence:


Negative only in May, hence the temperature will be below 0ºC between May and August.
To learn more about sinusoidal function, you can take a look at brainly.com/question/18055768