Why not use the Helper Lines ? ;)

Sorry i can't record! :(
Move
Select the red Rectangle Right Click
Make a vertical Helper Line on the black rectangle (on the right edge)
Click the little "trapezoid form" / Relocate Line
Type 100 (move on the right the Helper line it will blocked at 100 from the black rectangle Click

Pick Base Point (of the Red rectangle)
Move the red rectangle on the left to the Helper line for the target Point!

All that is made on one second! :)