Answer:
A: 35
Explanation:
DG is the combined segments DO and OG. In other words: 

We know that DG is 60. DO is (4x-3) and OG is (2x+21). So, substitute: 

Solve for x. Combine like terms: 

Subtract 18 from both sides: 

Divide both sides by 6. Hence, the value of x is: 

GO is defined as (2x+21). 
So, to find GO, we can now substitute 7 for x and evaluate. Therefore: 

Hence, our answer is A.