Rotation is a given a rigid motion or transformation which refers to movement of a figure around a center of rotation.
On this problem is given that the points representing the vertices of a triangle were rotated by a 180 degree counterclockwise rotation, which means a rotation on the opposite direction that the hands of a clock rotate or move. In this exercise it is asked to find the coordinates of the new vertices after the 180 degrees counterclockwise rotation, which is define by the rule (x,y)--(-x,-y)
To find the vertices of the image triangle, you should substitute the points of the preimage into the previous mention rule.
Since you know that 4/9 and 1/5 are used, make them common denominators. So 4/9 would turn into 20/45 and 1/5 would be 9/45. It results in 29/45, but that is the amount spent, so you would subtract 45-29/45, resulting in 16/45. For B, you know that she spent 3/4 of the savings, so you know that 1/4 is not being spent. So use 1/4 multiplied by 16/45 from part A to get 4/45. For C, you know that 4/45 is $100, so I multiplied 45x100 to get 4500 and then divided by 4 to get 4500/4.