The number of fish in a lake decreased by 25% between last year and this year. Last year there were 60 fish in the lake. What is the population this year?

This population, the population is 45 fish.

Step-by-step explanation: This problem can be solved by a rule of three.

Last year there were 60 fish in the lake. That was 100, that is, decimal 1.

This year it decreased 25%. So there 100%-25% = 75%, that is decimal 0.75. So

60 fish - 1

x fish - 0.75

This population, the population is 45 fish.

step-by-step explanation:

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0