Iwill give brainliest and 5 stars to correct answer and if you show your work

We see that:



So this is an arithmetic sequence with common difference d = -5. We can calculate the sum of that sequence as:

Sum = (first term + last term) * number of terms/2

first term = 1
number of terms = 12

last term = a₁₂ = ?

We know that:



so:



And sum: