The summation notation in the image is:

$\sum_{j=1}^{2} (5j)$

This means you sum the expression $5j$ as $j$ takes on the integer values from $j = 1$ to $j = 2$.

Step-by-Step Solution:

1. For $j = 1$: $5 \cdot 1 = 5$

2. For $j = 2$: $5 \cdot 2 = 10$

3. Add these results: $5 + 10 = 15$

Final Answer:

$\sum_{j=1}^{2} (5j) = 15$

Would you like me to explain more about summation notation or work on related examples? Let me know!

Related Questions:

1. What is the result of $\sum_{j=1}^{3} (5j)$?
2. How do you generalize $\sum_{j=1}^{n} (5j)$ for any $n$?
3. What is the meaning of summation notation, and where is it used?
4. How can you compute $\sum_{j=1}^{4} (2j + 3)$?
5. Can you write the sum of $5j$ using a formula instead of calculating it step by step?

Tip:

To simplify summations of linear expressions like $5j$, remember the formula for the sum of the first $n$ natural numbers: $\sum_{j=1}^{n} j = \frac{n(n+1)}{2}.$