(7 - 9i)(12 + 3i)(-5 - 3i)

I know the answer is -816 + 102i but I need help with the steps

5 tens and 8 ones gives 58

Step-by-step explanation:

We have to describe 58 as a sum of tens and ones

We know that first digit from the right is the ones place

Second digit is the tens place

Hence, 5 tens and 8 ones gives 58

Also, we can see that

10+10+10+10+10=50   (5 tens)

and 1+1+1+1+1+1+1+1=8 (8 ones)

on adding both we get 58

Hence, 5 tens and 8 ones gives 58