Dividing by whole numbers how do i do this

The answer is 6.7
You (should) know 10 goes into 67, 6 times. So write 6 on the top and subtract 60 from 67. You get 7. 10 doesn't go into 7 because 7 is less. So write a zero next to the 7 AKA bring down a 0. You will then technically have 70. 10 goes into 70, 7 times, so write 7 next to the previous 6 at the top, and put a decimal between 6 and 7.

Or

You should know if anything is being divided by 10. You just move the decimal to the left. Left is less. In 67 the decimal is right after the 7. 67.0. Therefore if you move the decimal one place over to the left you get 6.7

Either way works.

Aand b are correctly balanced reactions. they have the same number of atoms in both sides of the reaction