90+2 so 9 tens and 2 ones
10+10+10+10+10+10+10+10+10+10 = 9 tens or 90
1+1= 2 ones or 2
The 1st 1 I think is 26 and the 2nd one should be -14
There are 10 total digits ( 0, 1 , 2, 3, 4, 5, 6, 7,8 ,9)
1st digit can be 1 of 10
2nd digit can be 1 of 9 ( 10-1 because a number cannot repeat)
3rd digit can be 1 of 8 ( 9-1 because no number can repeat)
total combinations = 10 * 9 * 8 = 720
No, 243 is not a prime number, it is a composite number.
I hope I helped you again :-)
