Answer:
If adding, 43.2.
If subtracting, -34.2.
If multiplying, 174.15.
If dividing, 8.6.
Explanation:
Addition: Line up and add.
Subtraction: Add the first number and opposite of the second. 4.5+(-38.7)=-34.2.
Multiplication: Multiply as normal, count up how many decimal places are in the factors (2), and add that to your answer, 174.15.
Division: Turn both number into whole numbers by multiplying by 10. Then divide 387/45= 8.6.
CAN EXPLAIN FURTHER