As the error indicates, you have a string representation of a tuple '(-10, 0)', which you need to convert into an actual tuple (-10, 0), such as by using the eval() function.
PsychoPy does its best to import numbers from conditions files, but you presumably have cells in that file containing (-10, 0). Since that contains non-numeric characters, PsychoPy can’t mind-read what is intended, and so imports it as a character string. You then have the responsibility to convert it into the appropriate class as required, e.g.
image_3.setPos(eval(posit))
You could avoid this by splitting the two coordinates into separate columns (say x and y), and then specify things like this:
image_3.setPos(x, y)