Respuesta :

3.6 - (-1.5) + (-6)   -> 3.6-(-1.5) is the same is 3.6 + 1.5. 

Tip: -(- looks like a + 

So, 
3.6 - (-1.5) + (-6)
3.6 + 1.5 + (-6)
5.1 + (-6)
5.1 - 6
= -0.9