Answer
70
Work Step by Step
42$\div$0.6
Move the decimal in 0.6 to make it a whole number (6). To accommodate for this, add one per to 42 (420).
420$\div$6
Use long division to divide this, and the answer will be 70.
Alternatively, notice that 42$\div$6 = 7, and that 420 = 42 * 10, so 420$\div$6 = 7 * 10 = 70.