Hi does anyone low the answer 3d= 40.8

How to do this , and can some one explain

Fatima plans to spend at least $15 and at most $20 dollars on sketch pads and pencils. if she buys 2 sketchpads, how many pemcils can she buy while staying in her price range? fatima can buy between and pencils. ? (type whole numbers. use ascending? order.)

Cole says the distance between points (-5,0) and (0,-5)is 5 units. is he correct? explain why or why not.