9 is what percent of 10

Solve the following pair of equations for x and y: ax/b_ by /a= a +b; ax - by = 2ab

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.

Sioux co. replaced the roof on its existing building, therefore increasing the building's life by 10 years. the cost of the roof is considered a(n):