Ok, so they want an equation to help determine how many hour she must work to take home $450 dollars if she saves all of her earnings We will let x represent the work hours
10x - (10x * .25) = 450
Now solve for x 10x - (10x * .25) = 450 10x - 10x * -.25 = 450 7.5x = 450 7.5x/7.5 = 450 / 7.5 x = 60
So she will need to work 60 hours.
If you need help understanding how I derived at this conclusion, let me know.