E’zoza va Barnodagi pullarning nisbati 7:3 edi. E’zoza pulidan Barnoga bergach, E’zozadagi pulning Barnodagi pulga nisbati 7:13 bo‘lib qoldi. Shundan so‘ng Barnodagi pul E’zozanikidan 20 400 so‘mga ko‘p bo‘ldi. E’zoza Barnoga qancha pul bergan?

Boshlang‘ich pullarni nisbatga ko‘ra belgilaymiz: E’zozada 7x so‘m, Barnoda 3x so‘m bo‘lgan. E’zoza Barnoga bergan pulni y so‘m deb olamiz.

Berilgandan keyin pullar nisbati 7:13 bo‘lgani uchun:

\[\frac{7x-y}{3x+y}=\frac{7}{13}\]

Ko‘paytirib, y ni topamiz:

\[13(7x-y)=7(3x+y)\]

\[91x-13y=21x+7y,\quad 70x=20y,\quad y=3.5x.\]

Shundan keyingi pullar farqi 20 400 so‘m:

\[(3x+y)-(7x-y)=20\,400.\]

y=3.5x ni qo‘yamiz:

\[3x+3.5x-7x+3.5x=20\,400,\quad 3x=20\,400,\quad x=6\,800.\]

Demak, E’zoza bergan pul:

\[y=3.5\cdot6\,800=23\,800\text{ so‘m}.\]

Javob: E’zoza Barnoga 23 800 so‘m bergan.