4 DC || MN AD = 11 M 4 D A x N 5 C

Т.к. \(DC \parallel MN\), то \(\triangle AMN \sim \triangle ADC\) (по двум углам).

$$\frac{AM}{AD} = \frac{AN}{AC}$$,

$$\frac{AD - MD}{AD} = \frac{x}{x+5}$$,

$$\frac{11 - 4}{11} = \frac{x}{x+5}$$,

$$\frac{7}{11} = \frac{x}{x+5}$$,

$$7(x+5) = 11x$$,

$$7x + 35 = 11x$$,

$$4x = 35$$,

$$x = \frac{35}{4} = 8.75$$.

Ответ: 8.75