Which transformation will be equivalent to rotating a figure 90° counterclockwise

Reflecting over the x-axis and then reflecting over the line y = x.  

Step-by-step explanation:

A rotation 90° counterclockwise will map every point (x, y) to (-y, x).

Since the x- and y-coordinates are switched, this is not a reflection across the x-axis followed by a reflection across the y-axis.

Since the y-coordinate is negated and the x- and y-coordinates are switched, this is not a translation.

Reflecting across the x-axis will negate the y-coordinate, giving us (x, -y).  Following this with a reflection across y=x will switch the coordinates giving us (-y, x).  This is the correct transformation.