The linear equation shown below expresses the revenue of a café based on the number of children and adults who ate there last Tuesday.
10x + 15y = 180
x = number of children
X

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.