Answer:
23
Explanation:
Compatible numbers : numbers that are easy to add, subtract, multiply, or divide mentally. They are close in value to the actual numbers, although they do not necessary need to be rounded numbers.
-138 is close to -137.56
-6 is close to -6.12

Divide the top and bottom by -2:

Divide the top and bottom by 3

If this is too difficult to divide mentally, you could use -140 and -7:

As 2 x 7 = 14, then 20 x 7 = 140, so the answer is 20.