How do you multiply by two -digit number? ?

It's easier to put the bigger number on the top. You look at the digits like so: 19 times 15. Look at the last numbers in the problems (9 and 5) and multiply them which is 45. Put your 5 and carry your 4. Noe the tricky part is: you will multiply 5 times 1 then ADD the 4 you carried. So the final number for the first row will be 95. Then you put a place holder (0 or x) under the 5 in 95. Now you look at the 1 in 15. 1 times 9 is 9. Put your 9 beside your place holder. Now do 1 times 1 which is 1. Out that beside the 9. So noe all you're doing is adding 95+190=280. Inbox me if you need more help, I'll be glad to help :)

Ihonestly don’t no that