Ive been on this test for 3 hours so if you know anything about trigonometry please help

F(x) = 1/x g(x)=x-4 can you evaluate (g*f)(0) ? why or why not?

Which best explains why this triangle is or is not a right triangle ?

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?