It's the decimal points that are confusing you, isn't it? There are a number of approaches, but the first thing to do is to move the decimal point in the divisor 2.8. Move it one place to the right to get 28, and move it one place to the right in the dividend to get 678.2. Now you can split 28 into its factors 4 and 7, and divide by one then the other like so: by 4: 678.2/4=169.55 then by 7: 169.55/7=24.22142857... (Easier to divide by 4 first so that you have a smaller number to divide by 7.) A quick explanation of how you divide the decimal: when dividing 678.2 by 4 you get 169 and you haven't finished because you have 2 to carry and you've just met the decimal point, right? Ignore the decimal point but write the next number in the quotient with a decimal point in front of it and carry on: 169.5. You still have 2 over, so bring down a zero to make it 20 and divide again to get another 5: 169.55. Do the same when you're dividing by 7 and keep bringing down zeroes with each remainder. The number goes on forever, so stop when you have enough decimal places or you get fed up!
The other approach is to use long division, bringing in the decimal point as above. Long division will take you longer than splitting into factors because you probably won't know your 28 times table as well as you know your 4 and 7 times tables.