72 times what gives you 6834

What is the solution of sqrt x+2-15=-3

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.

Idon't get undoing if its pass adding and subtracting so can someone ? x-2 over 5 = 18