Answer:
15
Step-by-step explanation:
Let's call the mystery number x.
Hope this helps!
B: a = 1, b= 7, c = -2
Explanation:
Knowing This:
<u>solve for b</u>
<u>solve for a</u>:
<u>solve c</u>:
204 /6 = 34
29 +31 +33 + 35 +37 +39 = 207
4th number = 35