Answer:
6.25 colonies of bacteria per +pH change from 7 to 9
Explanation:
It seems to go from 57.5 to 70 or maybe 57 or 58
Either way I will go with my guess of 57.5
Rate of Change= (70-57.5)/(9-7)=(12.5)/(2)=6.25 rate of change for colonies of bacteria per positive pH change from 7 to 9