We are asked to write the appropriate number of decimal places in each sum, difference, product, or quotient.
Problem 1:

As you can see, the result of the above difference has only 1 decimal number.
Problem 2:

As you can see, the result of the above product has 3 decimal numbers.
Problem 3:

As you can see, the result of the above quotient has 0 decimal numbers.
Problem 4:

As you can see, the result of the above sum has 2 decimal numbers.
Problem 5:

As you can see, the result of the above product has 3 decimal numbers. (3,9