25
8 tens.
4/-3 8
1 tens and 2 0nes
500+10+6 = 516
(3*10)+(9*1)=39
8 tens and 4 one
If you have to have at least one group of each, there are four.
Oh, dude, it's like super easy. So, you start with 78, right? And then you regroup 1 ten as 10 ones. So, you take 1 from the tens place and add it to the ones place, making it 8 tens and 18 ones. See, easy peasy lemon squeezy!
To take the tens place and add it to the other tens
44
30+14=44