Final answer:
To solve the problem, we need to set up and solve a system of equations using the given information. After solving the system of equations, we find that Raul invested $600 at 4% and $900 at 6%.
Step-by-step explanation:
To solve this problem, we can set up two equations using the given information. Let's say Raul invested x dollars at 4% and y dollars at 6%. The interest earned from the 4% investment would be 0.04x and the interest earned from the 6% investment would be 0.06y. According to the problem, the total interest earned is $72, so we can write the equation:
0.04x + 0.06y = 72
Since Raul invested a total of $1500, we can write another equation:
x + y = 1500
We now have a system of equations that we can solve to find the values of x and y. Using substitution or elimination, we can find that x = $600 and y = $900. Therefore, Raul invested $600 at 4% and $900 at 6%.