Two workers

One worker needs 40 hours to do a job, and the second would do it in 30 hours. They worked together for several hours, then the company recalled the second, and the first completed the job in 5 hours. How many hours did they work together, and how much did each of them do?

Correct answer:

x =  15 h
a =  1/2
b =  1/2

Step-by-step explanation:

$$\begin{gathered} x\cdot (\frac{1}{40}+\frac{1}{30})+\frac{5}{40}=1 \\ x\cdot (1/40+1/30)+5/40=1 \\ 7x=105 \\ x=\frac{105}{7}=15 \\ x=15=15\text{h} \end{gathered}$$

$a=\frac{x+5}{40}=\frac{15+5}{40}=\frac{1}{2}=0.5$

$b=\frac{x}{30}=\frac{15}{30}=\frac{1}{2}=0.5$

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