I am sure someone will post an algebra-based solution soon. [Ha! I stand corrected. I just saw that you posted this question in another thread where someone has ALREADY posted algebra-based answers.] Here are two other approaches:
You can play with numbers that add up to 60, looking for the remaining minutes to be 1/4 of what has been played. For example...45 played, 15 left is wrong. It adds up to 60 but 15 is not 1/4 of 45. So try new numbers. Soon, you will land on 48 played, 12 remaining. Thus, 48 out of 60 minutes have been played, which is 4/5 or 80%.
You could also just try the answers.
For example, say you try 25%. That’s 25% of 60 which is 15 minutes played, 45 remaining – clearly wrong.
When you get around to trying 80% played, that’s 80% of 60 = 48, leaving 12 minutes to play. And since 12 is 1/4 of the 48 that have already been played.
Also, with Prepscholar once it thinks you’ve mastered something, you get no more problems like that. It makes it hard to review your old material then. it’s hard for me to imagine getting into the 1500s with that system. We used it and it was great up to about 1400, but without the extra review it seems really hard to push it further.
For the SAT Writing & Language Section, I’d recommend getting some practice on this free online resource with concept based questions and video explanations that are quite helpful. A few hours a day will really pick your score up. It’s called www.aethinks.in