Question 1135706
Use the Law of Sines:
{{{b/sin 30 = a/sin 70}}}
...which we know is:
{{{15/sin 30 = a/sin 70}}}
Cross-multiply:
{{{a * sin 30 = 15 * sin 70}}} 
Simplify:
{{{a(0.5) = 15(0.939693)}}}
{{{a(0.5) = 14.095395}}}
{{{a = 28.19079}}}