The sequence you've provided is an arithmetic sequence, where each term decreases by 5. To find the term that equals $-15$, we can use the formula for the $n$-th term of an arithmetic sequence:

$a_n = a_1 + (n-1) \cdot d$

Where:

• $a_n$ is the $n$-th term,
• $a_1$ is the first term (which is 50),
• $d$ is the common difference (which is -5),
• $n$ is the term number.

We need to find $n$ such that $a_n = -15$.

$-15 = 50 + (n-1) \cdot (-5)$

Now, solve for $n$:

$-15 = 50 - 5(n-1)$

$-15 = 50 - 5n + 5$

$-15 = 55 - 5n$

$5n = 55 + 15$

$5n = 70$

$n = \frac{70}{5} = 14$

So, the 14th term of the sequence is $-15$.

Would you like more details or have any other questions?

Here are 5 related questions:

1. What is the sum of the first 14 terms of this sequence?
2. How would the sequence change if the common difference was -10 instead of -5?
3. What would be the 20th term of this sequence?
4. How many terms are required for the sequence to reach a value less than $-100$?
5. Can you find the general form for the $n$-th term of this sequence?

Tip: When working with arithmetic sequences, always check if the common difference is positive or negative, as it determines if the sequence is increasing or decreasing.