I need help with 7 and 8, Round and/or estimate then add (nearest hundred) for both attachment below

Solve -.016x= -16. need solving this

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.

How can constraints be used to model a real-world situation?