The moon is about 24 miles from earth what is this distance written as a whole number multiplied by a power of ten

Which function is shown in the graph below?

Haruka hiked several kilometers in the morning. she hiked only 66 kilometers in the afternoon, which was 25% less than she had hiked in the morning. how many kilometers did haruka hike in all?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?