The amount invested at 4% is $4,200. This problem can be solved by using two linear equation with two different variables which represent the investment's partition and the investment's return. The first equation is x+y=$7,600 and the second equation is 0.04x + 0.05y=$338, then you must substitute the y variable in the second question with the first equation (0.04x + 0.05($7,600-x)=$338). Therefore, you will get a new equation to solve the problem which is 0.04x+380-0.05x=338 resulting x=$4,200.
