Line 3
since he added which is against the order of opreation rule he was supposed to multiply first then add
again what he was supposed to do is
Line 2:21+5+6(2)
Line 3:21+5+12
Mean is when you take all the numbers and add them together and divide by the amount of numbers there
Example: Find the mean of :3,4,6,7
So you a 3+4+6+7=20 divide that by 4(because there you added 4 numbers) and that equals 5
