Locating -1.5 on a number line is the same as locating 1.5 because both numbers are the same distance from zero, but in opposite directions. The numbers also have the same absolute value.
Locating -1.5 and 1.5 is different because -1.5 can be found to the left of zero (because it is a negative number) while 1.5 is found to the right of zero (because it’s a positive number).