Ответ:

a + 2l = 330

\frac{a+2l}{2} = \frac{3.5a}{2} + r

a + 2l = 3.5a + 2r

330 = 1.5a + 2r

l^2 = r^2 - \left(\frac{a}{2}\right)^2

\frac{l}{a/2} = \frac{4}{3+4} = \frac{4}{7}

l = \frac{4a}{7}

330 = 1.5a + 2 \cdot \frac{l^2 + \left(\frac{a}{2}\right)^2}{2l}

7a^2 - 2640a + 44800 = 0

Объяснение: