Question

Two mechanics worked on a car. The first mechanic worked for 10 hours, and the second mechanic worked for 15 hours. Together they charged a total of $1900. What was the rate charged per hour by each mechanic if the sum of the two rates was $155 per hour?

Answer 1

For this case we propose a system of equations:

Let "x" be the variable that represents the hourly rate of the first mechanic.

Let "y" be the variable that represents the hourly rate of the second mechanic.

We have to:

$10x + 15y = 1900\\x + y = 155$

We clear "x" from the second equation:

$x = 155-y$

we substitute in the first one:

$10 (155-y) + 15y = 1900\\1550-10y + 15y = 1900\\5y = 1900-1550\\5y = 350\\y = \frac {350} {5}\\y = 70$

Thus, the second mechanic charges $ 70 per hour.

$x = 155-70\\x = 85$

So, the first mechanic charges $ 80 per hour,

Answer:

The first mechanic charges $ 85 per hour,

The second mechanic charges $ 70 per hour.

Answer 2

When you are looking for the answer in this type of scenario you do.
I=PRT (interest = price•rate•time)

I = $1900•$155•25 (you add the two times)
I = $7,362,500

Hope this helps.