The given question is a multiplication problem where 10 is multiplied by 9. When multiplying a two-digit number by a one-digit number, we start by multiplying the ones place of the two-digit number by the one-digit number. In this case, multiplying 9 by 0 gives us 0. Then, we multiply the tens place of the two-digit number by the one-digit number. Here, multiplying 9 by 1 gives us 9. Finally, we add the two products together to get the final answer, which is 90.