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7. Luis and Roberto are donating some of their baseball cards to the library. Luis startedwith 50 cards and gave away X number of them. Roberto started with 80 cards andgave away 3 times as many as Luis had given away.If they now have the same number of baseball cards, what equation could you use tofind the number of cards that Luis gave away?

Respuesta :

We can write the amount of cards that Luis keep as:

[tex]50-x[/tex]

For Roberto, this is:

[tex]80-3x[/tex]

(x is the amount of cards Luis gave, so 3x is the amount of cards Roberto gave away)

We know that the amount kept by the two is the same, so we have:

[tex]\begin{gathered} 50-x=80-3x \\ -x+3x=80-50 \\ 2x=30 \\ x=\frac{30}{2} \\ x=15 \end{gathered}[/tex]

The number of cards that Luis gave away is 15 cards.