Good question, below is my method (taking initial average speed as 's', initial time as 't' and distance as 'd' which is constant)
Statement 1: When s changes to s+10, t changes to t-5. No we know, initially for steve, d=s*t. with the given info, it will be, d=(s+10)*(t-5). so, s*t = s*t+10t-5s-50 => 2t-s=10. Two variables, one equation. Insufficient.
Statement 2: When s changes to (s+1/2s) and t changes to (t-1/3t). Again the initial equation for distance is, d=s*t. with given info it becomes,
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Statement 1: When s changes to s+10, t changes to t-5. No we know, initially for steve, d=s*t. with the given info, it will be, d=(s+10)*(t-5). so, s*t = s*t+10t-5s-50 => 2t-s=10. Two variables, one equation. Insufficient.
Statement 2: When s changes to (s+1/2s) and t changes to (t-1/3t). Again the initial equation for distance is, d=s*t. with given info it becomes,
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