Luis rides his bicycle 3/4 mile in 15 minutes, or 1/4 hour, along the bike trail. Assuming he rides at a constant rate, what is his speed, in miles per hour?

Bob is putting books on a shelf and takes a break after filling 18 1/2 inches on the book shelf. the book shelf is now 2/3 full. how long is the entire bookshelf?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap