Tanya and keisha volunteer at the hospital after school. a local company has promised to donate one quarter to the hospital for every hour a student volunteers during the year. by the end of the year, tanya and keisha together have earned $58.50 for the hospital. keisha volunteered twice as many hours as tanya.

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.