Can I use a 235/55 18" (originally from a Lexus SUV) on my 07 ford edge who's tires are 245/60 18"?

The width of the tires is slightly different (by 1cm) which may or may not matter but the speedometer and odometer will not be entirely accurate. The 55 vs 60 expresses the percentage of the width that the sidewall is tall. So in one case the sidewall height is 55% of 235mm whereas the other is 60% of 245mm. Whatever that difference calculates to needs to be doubled and multiplied by 3.14 (I.e. pi) to determine how far off the circumference will be from the original size. The new tire you suggest would be traveling slightly further per rotation than the car thinks it is. Therefore your odometer would read slightly too few miles and the speedometer would read slightly too slow.

Correction: The 235 55 is the new tire so the car would read slightly fast and slightly high on the odometer.