Yes.
a test for a function is the vertical line test, so think about drawing a vertical line on top of this picture. if at any point the line is touching the graph more than once, it is not a function. this graph passes the vertical line test
Let's say that the value invested in the account with a rate of 8% is "x", then the amount invested in the account with a rate of 12% is:

To calculate the total interest we need to calculate the interest of each individual account and sum them:

The total interest is the sum of the two expressions above:

The value invested in the account with 8% interest is 830, the one invested in the account with 12% interest is 1280.
.00084 in scientific notation is 8.4 × 10^-4