Explanation:
Since this is an isosceles triangle, the angle at G is the same as the angle at P. Thus G=(x+10)°.
Remembering that the sum of a triangle adds up to 180°.
Therefore,
3x + (x+10) + (x+10)=180.
5x + 20 = 180
5x = 160
x=32
Remember, G=x+10
G= 32+10
G=42°