Please help Solving linear and quadratic equations

What is the effect on the graph of the parent function f(x) = x when f(x) is replaced with 3f(x)? a) shifts the line 3 units up b) shifts the line 3 units down c) increases the slope of the line by a factor of 3 d) decreases the slope of the line by a factor of 3

Compute the standard deviation of the following set of data to the nearest whole number. 10, 10, 15, 20, 25

Which statement is true about the function f(x)= square root -x ? the domain of the graph is all real numbers. the range of the graph is all real numbers. the domain of the graph is all real numbers less than or equal to 0. the range of the graph is all real numbers less than or equal to 0.