This question is an example of a compound percentage decrease.
To work this out you would first need to convert the percentage of 25 into a decimal. You can do this by dividing the percentage of 25 by 100, this gives you 0.25. This is because percentages are out of 100.
The next step is to minus 0.25 from 1, this gives you 0.75. This is because we are working out the percentage decrease.
The final step is to multiply the amount of 900 by 0.75 to the power of 7, this gives you $120.14.
so basically, 25% of the 100% value is gone, right? which means that 75% of the value would remain. After that, all is easy. 8000*0.75, since 75% is 0.75, and the answer of that is 6000, so the current value is 6000 dollars.