Question

Daca la dublul unui numar natural n adunam sfertul lui, obtinem un numar cu 25 mai mare decat numarul initial. Aflati n

Answer 1

2n+n/4=n+25;
⇒8n/4+n/4=n+25
⇒9n/4=n+25
⇒25=9n/4-n
⇒25=9n/4-4n/4
⇒25=5n/4
⇒n=4·25/5
⇒n=4·5⇒n=20;

Answer 2

$2a+a/4=a+25 amplificam \\ 8a/4+a/4=4a/4+100/4 \\ 9a-4a=100 \\ 5a=100 \\ a=100:5 \\ a=20$