0=-10 this is not possible so the answer is no solution
You can draw lines from the center of the hexagon to the peak. And you can find that this hexagon is divided to 6 parts. Every 60° can the hexagon map onto itself. So at 60,120,180,240,300 and 360 total 6 times.
If the bacteria is tripling every 10 minutes, that means the "rate of increase" on that period is 200%, so if say the current amount is "c", 200% of "c" is just 2c, so c + 2c is 3c, a tripled amount.
The answer of the next term is 31