if he were to bring over 64 in line 3 to the other side in line 4, it should be divide instead of minus
There is a mistake at Line 4.He should not minus 64 on both side because on the RHS, it is multiplied by m and 1/2 so, it should be 160/64 = 1/2 x m.
There is a mistake form line 3 to 4, the mistake is in 160-64=96 it should be 160/64=2.5 as *64 is a multiplication not an addition.
When shifting the 64 from the RHS to the LHS, the sign is supposed to change from times to divide and not minus.
In line 4, it should be 160/64 = 1/2 x m.