$157.50 would be the amount that you earn in interest
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.
1584 lightbulbs would be defective out of 4400
The simplified version of this equation would be
-x + y
2 hours of a 60mph is literally 60 miles per hour so for 2 hours its 120miles plus an addition of 40 miles how ever its half an hour so he gained 20 so 140 should be the answer if im not mistaken.