Answer:
Zander starts with 7,000; Carly starts with 5,000
Step-by-step explanation:
1 - Visually solving
Looking at the final value (31,000) one could interpret the sums of the numbers tripled and doubled respectively would need to equate to 31,000.
Taking off the additional zeros could also prove beneficial. To get 31, one of the numbers tripled or doubled would need to either be 11 or 21. 11 is a prime number, so that can be cancelled out. 7 multiplied by 3 (triple) produces 21.
12 - 7 = 5. Solving for the leftover 5 which would be doubled, you would get 10.
10 + 21 = 31.
2 - Algebra
x - Zander; y - Carly
To begin with you should need the initial formula.
x + y = 12,000
Your second formula would then take into consideration the changes made to x and y
3x + 2y = 31,000.
Using process of elimination or substitution, (either method works), you will find x = 7,000 and y = 5,000
, and 
, we have
