Question 388309
Use the sine rule,
{{{c/sin(C)=a/sin(A)}}}
{{{12.8/sin(24.6)=30.7/sin(A)}}}
{{{sin(A)=0.9984}}}
{{{highlight(A=86.78)}}}
Then 
{{{A+B+C=180}}}
{{{86.78+B+24.6=180}}}
{{{highlight(B=68.62)}}}degrees
Then using the law of sines again,
{{{c/sin(C)=b/sin(B)}}}
{{{12.8/sin(24.6)=b/sin(68.62)}}}
{{{highlight(b=28.6)}}}