Answer:
-136
Explanation:
This series can be written as: (14 - 3*0) + (14 - 3*1) +...+ (14 - 3*n)
The sum of the first 16 terms is:
14*16 - 0 - 3 - 6 - 9 -... = 224 - 360 = -136
This underlined bit can be calculated in many ways, I personally used my calculator, but there are formulas to do so.