The given inequality is expressed as
0 < a < 6
This means that the values of a that would satisfy the inequality are numbers between 0 and 6 but both 0 and 6 are not inclusive. This would be shown by not making solid circles at 0 and 6. The number line is shown below
Let the amount invested at 4% be = x
Let the amount invested at 3% be = y
Given is:
or
.... (1)
As, total income for the two investments is $194, so equation is:
....(2)
Putting value of x from (1) in (2)
And x=5200-y
Hence, money invested at 4% is $3800 and money invested at 3% is $1400