A store manager purchases a DVD for $15. He marks it up to $21.75 in order to make a profit. What is the percent of increase?

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

Sorry guys but as you have a small brain

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=