A first number plus twice a second number is 21. Twice the first number plus the second totals 15. Find the numbers.

Respuesta :

Answer:

The first number is equivalent to 3

The second number is equivalent to 9

Step-by-step explanation:

[tex]n_{1}+2n_{2} =21\\2n_{1} +n_{2} =15\\\\2n_{1} +n_{2} =15\\2(2n_{1} +n_{2}) =(15)2\\4n_{1} +2n_{2} =30\\2n_{2}=-4n_{1}+30[/tex]          Now, plug this equation in to the first equation

[tex]n_{1}+2n_{2}=21\\n_{1}-4n_{1}+30=21\\-3n_{1}=-9\\n_{1}=3[/tex]           Now, plug this number in to either equation

[tex]2n_{1}+n_{2}=15\\2(3)+n_{2}=15\\6+n_{2}=15\\n_{2}=9[/tex]