It is the number that multiplies the unknown variable
x+6
x+9x
It is the coefficient of the unknown variable
v + 6
Let x be the unknown number. the expression is: x + 10.
5+4x
2x+15
The algebraic expression is n + 100, where n is the unknown number.
Let the unknown number be x and so the expression is: x+12
n/6 + 3
As an algebraic expression this is written 2x - 12, where x is the unknown number.