SOLUTION: Robin has 21 books on computers. She donates z of them to the school library. How many does she have left?

Algebra.Com
Question 748579: Robin has 21 books on computers. She donates z of them to the school library. How many does she have left?
Found 2 solutions by timvanswearingen, Cromlix:
Answer by timvanswearingen(106)   (Show Source): You can put this solution on YOUR website!
She started with 21 and got rid of, or subtracted z:

Answer by Cromlix(4381)   (Show Source): You can put this solution on YOUR website!
(21 - z)would be the number of books left.
RELATED QUESTIONS

Emma has 105 books. She donated 1/3 of her books to the second grade library. The second... (answered by Boreal)
ellise is finishing 2nd grade she goes to school 147 days per year and has 10 years left (answered by solver91311)
Mia has four math books, three novels and two books of poetry. She wants to arrange them (answered by sudhanshu_kmr)
Joann is placing books into boxes to prepare for a renovation of the school library.... (answered by josmiceli)
Presley is organizing the school book sale. Each stall will have 40 books on the shelf... (answered by macston)
Judy has 15 books in her library. She bought several books at a thrift store on Saturday. (answered by advanced_Learner)
In a school library, 52% of the books are paperback. If there are 2,658 books in the... (answered by Cromlix)
The books to Robins ratio of the number of Claudes is 5:6. The ratio of the number of... (answered by greenestamps)
i'm stuck on a few problems where i have tied many different equations and end up with a... (answered by ikleyn)