S and O are solving problems. For every three problems that S solves, O solves seven. Together, they solved 180 problems in seven days. How many problems did S solve that week?

Answer 1

Let P be the number of problems S solved and O solved 7/3 * P = (7/3)P problems.
Together they solved P + (7/3)P = 180 problems in 7 days.
Combining like terms, we get (10/3)P = 180.
Dividing both sides by (10/3), we get P = (3/10) * 180 = <<(3/10)*180=54>>54. Answer: \boxed{54}.