Arithmetic Sequence Problem: Finding Terms Before 10 with -3.5 Difference

To solve this problem, we will take the following steps:

• Use the information $a_3 = 10$ and the common difference $d = -3.5$ to find the earlier terms in the sequence.
• Apply the arithmetic sequence formula: $a_n = a_1 + (n-1) \cdot d$.

Let's apply these steps:

Step 1: Using the given formula for the $n$-th term in an arithmetic sequence, $a_3 = a_1 + (3-1) \cdot d = 10.$

Plug in the common difference $d = -3.5$:

$10 = a_1 + 2 \cdot (-3.5).$

Simplify the above equation:

$10 = a_1 - 7.$

Solving for $a_1$, we get:

$a_1 = 10 + 7 = 17.$

Step 2: To find $a_2$, use:

$a_2 = a_1 + (2-1) \cdot (-3.5) = 17 - 3.5.$

Thus, $a_2 = 17 - 3.5 = 13.5.$

Therefore, the first element is 17, and the second element is 13.5.

The solution to the problem is $13.5, 17$.