When solving the following system by elimination, which variable would be eliminated after adding the 2 equations together?

Mary used 1/7 of a spool of ribbon to complete 4 projects. she used the same amount of ribbon on each project. how much ribbon did she use on each project?

Henry is an avid reader, he devours 90 pages in half an hour how many pages has henry read per minute?

Michelle is planting flowers in her garden. she wants the ratio of daises to carnations to be 3 to 2. michelle wants to plant a total of 35 flowers. how many daises should she plant?