a very fast way to do it:
Trivially 8.8*5>10, so the power of 10 is 6+2+1 = 9.
Therefore, the answer is 
6x-2x^2 would be the answer
Let x = # of 25-cent stamps
y = # of 2-cent stamps
{ x+ y = 88
{ 0.25x + 0.02y = 15.56
60 25-cent stamps 28 2-cent stamps
We have that (x) + (x+2) + (x+4) = 126 so 3x + 6 = 126 can be used to find the first integer.
3x + 6 = 126
3x = 120
x = 40
The numbers are 40, 42, 44
Answer:
1200
Explanation:
Order does not matter, if we said xyz order, it would still not make a difference if it was zyx or yzx hence we use the combination formula:
nCr = n! / r! * (n - r)!
where n= total number of items
r= number of items chosen at a time
Combinations are used when the order of events do not matter in calculating the outcome.
We calculate using the formula:
(30×20×12)÷3!=1200
There are therefore 1200 ways for the three distinct items to not be in same row or column