10a- 4a= 6a 1) 6a+12
6xa= 6a 6x2=12 2) 6a+12
The expressions are equivalent. For the first sum, all you do is work out the total amount of a and what number is being added. However, on the second question, you have to expand the answer. I was taught a 'noddy method' to begin with. This should help.
