if Q is between A and M and QM=7.3 and AM=8.5, then Q=?

Segments on the same line add in length, so you have
... MQ + QA = MA
Subsituting the given information, you have ...
... 7.3 + QA = 8.5 . . . . . MA = AM
Subtract 7.3 from both sides of the equation.
... QA = 1.2
The appropriate choice is ...
... B. 1.2