we are given
△ABC
we can use area of triangle formula
[tex]A=\frac{1}{2} AB*BC*sin(B)[/tex]
we have
AB=6
BC=10
m∠B=120°
so, we can plug it
[tex]A=\frac{1}{2} 6*10*sin(120)[/tex]
[tex]A=\frac{1}{2} *60*\frac{\sqrt{3} }{2}[/tex]
[tex]A=15\sqrt{3} [/tex]..............Answer