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.
The answer would be the first one.
I find it easier to expand the equation (you still get the same answer).
= 2 * 7x + 2 * 3y + 2 * 3
= 14x + 6y + 6
Hope this helps!
Answer:
4,046.4 ft^{2}
Step-by-step explanation:
