Amy uses groups of 10 buttons to show her room number. she uses 15 groups of buttons with 4 left over. what is her room number?

15 points ! ~ see if you know the answer to both you!

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document

Which expression represent a number that is one fourth as great as 10-2a. (10-2)+4b. (10-2)÷4c. (10-2)-4d. (10-2)×4