For the 1st minute => 1 equation per 2 seconds
x equation per 6o seconds = 60/2 = 30 equations

For the 2nd minute => 1 equation per 1.5 seconds
x equation per 6o seconds = 60/1.5 = 40 equations

For the 3rd minute => 1 equation per 2 seconds
60 equations per 60 seconds

Total = 30 + 40 + 60 = 130 equations in 3 minutes.
Now, what is the minimum number of questions Danjie must answer correctly in the third minute in order to beat her previous high score?

Statement 1: Danjie's previous high score was reached by answering all the questions given in the first three minutes and getting 90% of them correct.
90% correct answers for the first 3 minutes = 90% of 130 = 0.9 * 130 =117 questions.
To beat her previous high score, Danjie must answer at least 118 questions.
To get at least 118 questions, Danjie must answer correctly 100% in 1st and 2nd minute = 40 + 30 questions = 70.
So, 118 - 70 = 48
Hence, she must answer a minimum of 48 questions to beat her previous high score. By this expression, statement 1 is SUFFICIENT.

Statement 2: If Danjie does not answer 100% of the questions correctly during the first minute and during the second minute, the game will not continue.
This means that Danjie experience "game over" in the first minute, and her high score is not up to 30 but the exact value for the previous high score is not known, hence, a minimum value needed to beat the high score cannot be evaluated. Therefore, statement 2 is NOT SUFFICIENT.

Since statement 1 alone is SUFFICIENT, the correct option is A.

Thanks