1.) 54.39 - 36.245

how do i solve this problem?

You have to subtract 54.39 - 36.245 = to 18.145

Set it up like this
54.390
-36.245
=18.145
Borrow from the 9 so the 0 becomes 10 and the 9 now becomes 8. Subtract 10-5=5 then 8-4=4 the. 3-2=1 and we borrow from the 5 so the 4 becomes 14, now you subtract 14-6= 8 and the 5 is now 4 so 4-3=1