Two trains

There were 159 freight wagons at the railway station creating two trains. One had 15 more wagons than the other. How many wagons did each train have?

Correct answer:

a =  87
b =  72

Step-by-step explanation:

$$\begin{gathered} a+b=159 \\ a=15+b \\ a+b=159 \\ a-b=15 \\ Row2-Row1\to Row2 \\ a+b=159 \\ -2b=-144 \\ b=\frac{-144}{-2}=72 \\ a=159-b=159-72=87 \\ a=87 \\ b=72 \end{gathered}$$

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