Final answer:
To solve the problem, set up a system of equations based on the given information and solve using the method of addition.
Step-by-step explanation:
To solve this problem, we can set up a system of equations based on the given information. Let x be the amount invested at 8% and y be the amount invested at 5%. The first equation is x = y + 1400, which represents that there is $1400 more invested at 8% than at 5%. The second equation is 0.08x + 0.05y = 840, which represents the total annual interest received.
We can now solve the system of equations using the method of addition. Multiply the first equation by 0.08 to make the x terms cancel out when added to the second equation:
0.08(x) = 0.08(y + 1400)
0.08x = 0.08y + 112
Add this to the second equation:
0.08x + 0.05y = 840
(0.08y + 112) + 0.05y = 840
0.13y + 112 = 840
0.13y = 728
y = 5600
Substitute this value of y back into the first equation to find x:
x = 5600 + 1400
x = 7000
Therefore, $7000 is invested at 8% and $5600 is invested at 5%.