Question

the answer is 144 but how?

Answer 1

the angles around the point a total 360°
the lines AB and AC make a sector of the circle.
we are told that the circumference of that sector is 2/5 of the total circumference
so 360/5 ×2 =144

Answer 2

x = 144°

the following ratio is true for the given circle

$\frac{arc}{circumference}$ = $\frac{x}{360}$

that is $\frac{2}{5}$ = $\frac{x}{360}$ ( since AB is 2/5 circumference )

cross-multiply

5x = 720 ( divide both sides by 5 )

x = 144