If

4+5+4+5=81 5+6+5+6=16 6+7+6+7=64 1+2+1+?=16

What is the missing number?

Third number is same as first one and fourth is same as second one in all the cases so the missing number is 2.

4+5+4+5=18, 1+8=9, 9*9=81 5+6+5+6=22, 2+2=4, 4*4=16

following the same logic... missing number is 0

Find a number which is Divided by 2 the balance should be 1, div by 3 bal 2, div by 4 bal 3, div by 5 bal 4, div by 6 bal 5, div by 7 bal 0, div by 8 bal 7.