Dr. evans just started an experiment. He will collect data for 7 days. How many hours is this?

Which one ? is the answer and how to find this answer

What is the answer to this question? i'm a bit stumped. also how do i do it? 5(x - 4) = 2(x + 5)

The marked price of an article is 25% above its selling price and the cost price is 30% less than its marked price . find the discount percent and gain percent. only a brainlest can solve it i will mark you brainlest