we know that
Vertical angles are congruent angles opposite each other where two lines cross
so
in this problem
m∠A=m∠B
so
substitute the values
[tex]x=3x-60\\3x-x=60\\2x=60\\x=60/2\\x=30\°[/tex]
therefore
the answer is
The measure of angle A is [tex]30\°[/tex]
