Answer:
5.6
Step-by-step explanation:
We assume that 7 is the measure of the portion of the secant that is inside the circle between the circle and the intersection with the other chord.
The product of segment lengths on the same chord is a constant for chords that intersect at the same point. That is, ...
10x = 8·7
x = 56/10
x = 5.6
_____
Comment on the geometry
If you draw the figure to scale, you find the geometry shown is impossible. The arc measures and chord lengths are incompatible.
