maths

Ann is X years old. David is 3 years younger than ann. Ken is twice as old as Ann. The total of their ages is 25. How old is ann?

$\text{Ann } = x \\ \text{David } = x - 3\\ \text{Ken } = 2 \cdot x \\ \text{Ann + David + Ken } = 25\\ \begin{array}{rcl} x + (x-3) + 2 \cdot x &=& 25\\ 4x - 3 &=& 25\\ 4x &=& 28 \\ \mathbf{x} & \mathbf{=} & \mathbf{7} \end{array}\\ \text{Ann is 7 years old } \\ \text{David is 4 years old }\\ \text{Ken is 14 years old}$

Thanks lad