We need to recall the formula to calculate the area of a rectangle, since we are dealing with a rectangular window:
Area of rectangle = width * length
therefore, since they give us the window's area: 6525 , and also the window's length: 87 cm, we just need to replace those values in the area formula and solve for the unknown "width". We do such by dividing both sides of the equation by 87 cm in order to isolate the unknown on one side of the equal sign;
Work out 9% of $87.00 then add theat to the $87.00 that will be the total cost. find how much cash she gave the cashier and then minus the total cost from that to find the change she got.
