Someone please help!!

Ten times the square of a non-zero number is eqaul to ninety times the number

The table represents a function f(x). what is f(3)? a.-9 b.-1 c.1 d.9

Due to bad planning, two of the local schools have their annual plays on the same weekend. while 457 people attend one, and 372 attend the other, only 104 people were able to attend both. how many people went to at least one play?