On the circumference of the figure with center O, y = 70 . ∠X = ?

1. Note that the angle \( y \) subtended at the center \( O \) is given by
y = 70^\circ .
For a circle, the angle subtended at the center is twice the angle subtended at the circumference.

2. Therefore, the angle \( \angle X \) at the circumference is
\angle X = \frac{y}{2} = \frac{70^\circ}{2} = 35^\circ .

Answer:
\angle X = 35^\circ