-3•(-5)+18:(-2)

To simplify the expression, we follow the order of operations (PEMDAS):

1. Perform the multiplication first: -3 * (-5) = 15
2. Then, perform the division: 18 / (-2) = -9

Therefore, the expression -3 * (-5) + 18 / (-2) simplifies to 15 - 9 = 6.