Respuesta :

popalabdulqayou
the double of an inscribed angle is equal to the central angle and central angle is equal to arc angle, therefore:
2(3x-1.5)=(3x+9)
6x-3=3x+9
6x=3x+12
3x=12
x=4
then plug it back to the first equation 3x+9, so, therefore 3(4)+9=21