Good question let me see if I can figure it out
I think the answer is he should've added t instead of subtracting t.
Hey there!
First add
60%+10%= 70%
So 70% will be taken off
Now multiply .7(which is the same as 70%) by 220
220*.7= 154
154 was taken off
220-154= 66
The Answer is $66
Hope this helps!:)