"decreased by" means "minus" 12 decreased by z means 12 - z It really is that simple.
The algebraic expression for 12 divided by a number is 12/x, where x represents the unknown number being divided into 12. This expression represents the quotient of 12 divided by the unknown number x. It can also be written as a fraction, 12 over x.
12
Let the unknown number be x and so the expression is: x+12
16
That depends on what the number is which you are decreasing by. It is a number less than or equal to 12. Beyond that nothing more can be said without further information.
It is: 12 ≤ N - 7
16
x + 12. If the unknown number is represented by x, the expression for a number increased by 12 would be x + 12.
12/x
n × 12
-(n/12)