Every triangle has 180 degrees. All 3 angles should add up to 180 no matter how they are composed.
x + x - 5 + 3x + 25 = 180 Rearrange so like terms are together
x + x + 3x - 5 + 25 = 180 Combine
5x + 20 = 180 Subtract 20 from both sides
5x + 20 - 20 = 180 - 20 Combine
5x = 160 Divide by 5
5x/5 = 160/5 Divide
x = 32
Find G
G = 3x + 25
G = 3(32) + 25
G = 96 + 25
G = 121