Answer:
180 gallons
Step-by-step explanation:
In order to calculate you just need to calculate the 10% of the herbicide that is being degraded in the first week, so we do a rule of three to calculate that 10%:
[tex]\frac{200}{100} =\frac{x}{10}\\ x=10*\frac{200}{100} \\x=20[/tex]
So the 10% is 20 gallons, and that is the gallons of herbicide that degraded in the first week, so we just withdraw the 20 gallons degraded from the initial 200 gallons:
200-20=180
So there will still be 180 gallons in the pond after one week.
