4. Robiyada bir nechta marka bor. Rustamda Robiyaga qaraganda ikki barobar ko‘p marka bor. Madinada Rustamnikidan ikki barobar ko‘p marka bor. Uchala bolada jami 210 ta marka bo‘lsa, Madinada nechta marka bor?

Robiyadagi markalar sonini \(x\) ta deb olamiz.

Rustamda: \(2x\) ta marka.

Madinada: \(2 \cdot 2x = 4x\) ta marka.

Jami: \(x+2x+4x=210\).

\(7x=210\), demak \(x=30\).

Madinadagi markalar soni: \(4 \cdot 30=120\) ta.

Javob: Madinada 120 ta marka bor.