One safe investment pays 10% per year, and a more risky investment pays 18% per year. A woman who has $144,800 to invest would like to have an income of $19,840 per year from her investments. How much should she invest at each rate?
10% $
18% $

It's like discovering the answer to a puzzle. the purpose in solving an equation is to find the value or values of the variable that makes it a true statement. any value of the variable that makes the equation true is called a solution to the equation.