I think 30??
Because if there are twice as much girls then 10*2=20 girls and 10 boys. So 20+10=30
Answer:
Step-by-step explanation:
y-y1=m(x-x1)
y-7=-2(x-6)
y-7=-2x+12
MAB is 120, so m∠ADB is half of mAB=60
AC is the diameter, which means arc ABC is 180, and m∠ADC=90
m∠BDC=m∠ADC-m∠ADB=90-60=30
so the angle BDC is 30 degree