Answer and explanation:
Given : Expression 'Thirteen is at least the difference of a number v and 1'.
To find : Write the expression ?
Solution : 
'Thirteen is at least the difference of a number v and 1'.
 "at least" means "greater than or equal to". 
The difference of a number v and 1 = v-1
 So, Number 13 is greater than or equal to the v-1
i.e. 

Solving the expression, 
Add 1 both side,

