Since HJ is tangent to circle G, it forms a right angle with the radius that intersects it.
This means HG and HG are perpendicular and we have a right angle.
We have a (right) triangle with angle measurements 43 and 90, and we want to find the value of the last angle.
All the angles in a triangle must add up to 180, thus we can create the following equation to find the measurement of the last angle:


The measure of angle G is 47 degrees. Let me know if you need any clarifications, thanks!