Budget Line Equation:

I = Qx x Px + Qy x Py where
I = Income, Q = Quantity, and P = Price

Gross Domestic Product (GDP):

GDP = C + I + G + NX
where GDP = Gross Domestic Product, C = Consumption, I = Investment, G = Government Spending, NX = Net Exports which is Exports - Imports.

Profit and Revenue:

P = R - C where P = Profit, R = Revenue, and C = Cost
Gross Profit Margin  =  Gross Profit
  Revenue

P = R - C where P = Profit, R = Revenue, and C = Cost
Net Profit = Gross Profit(1 - Tax Rate)

Net Present Value (NPV):

NPV = ΣPVt where PVt is denoted as
PVt  =  Ct
  (1 + i)t

where Ct is the cash flow at time t and i is the discount rate