Question

subtract -1.5-(-3.6)

Answer 1

Two negatives = +
Therefore, you have:
-1.5 + 3.6 = 2.1

Think of it as money, you have $3.60 (+3.6) , but you owe someone $1.50 (-1.5)

Answer 2

-1.5 - (-3.6) =
-1.5 + 3.6
Minus negative 3.6 equals positive 3.6