You have to use PEMDAS, by multiplying before you add. So when you multiply 5*6, you get 30 and add the remaining 27 to get 57.
To answer this you can use a guess and check strategy.
Start with 5 minutes using it (25% lost) and 10 minutes charging (20% gained).
Try 7 minutes using it (35% lost) and 14 minutes charging (28%).
Next, 9 minutes (45%) and 18 minutes(36%).
10 minutes (50%) and 20 minutes (40%). This is the difference.
She used it for 10 minutes and charged it for 20 minutes.
Answer: 17
Step-by-step explanation: ok so first to find the mean you add all the numbers then divide by how many numbers there is so basically 18 plus 15 plus 20 plus 15 then divide by 4 because there is 4 numbers and once you do that it is 17
6/7 × 4 would be the correct answer. This is because 6/7 × 4= 3 3/7 which is equal to 4/7 × 6= 3 3/7. No other expression would equal 4/7 × 6
