The total sum of interior angles in any quadriateral (a four sided shape) is 360°.
There are lines above the angle G and angle H. This indicated that both angles are equal because they have the same number of lines.
So you have two angles which you add together like so:
105 + 117 = 222°
Then we take this away from 360° to find out how many ° Is missing:
360 - 222 = 138°
Since both the angles are equal, you must divide 138° by 2 in order to find out one of the angles. This will split the remaining ° in half:
138/2 = 69°
Therefore angle G equals 69°.