You can
put this solution on YOUR website!
I assume you mean that those three angles are angles of
a triangle,
Since the sum of the three angles of any triangle is 180°,
We indicate their sum and set it equal to 180°
(x+64°)+(x+84°)+40° = 180°
Solve that and get x = -4°
Then use that value of x to find angle A. We can't help
you any further because we don't know what angle is
represented by A.
Edwin