Question

Two mechanics worked on a car. The first mechanic charged $55 per hour, and the second mechanic charged $60 per hour. The mechanics worked for a combined total of 20 hours, and together they charged a total of $1125. How long did each mechanic work?
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Answer 1

Answer:

15 and 5 hours.

Step-by-step explanation:

Call x the time taken by the first chap, and y the second.

$\left \{ {{x+y = 20 \atop {55x+60y=1125}} \right.$

Let's divide by 5 and play with the LHS of the first equation a bit:

$11x+ 11y +y = 225\\11(x+y)+y= 225$ we know how much x+y is ( first equation!) let's solve.

$11(20) +y = 225 \rightarrow y=5$ At this point it's easy to check that $x=15$