How do you define a variable and write an expression for each phrase: three less than d?
A variable represents a value that is unknown or can change.
d -3 = three less than d. less means subtract.
The English word variable means changeable. Like the weather is variable today. There is going to be sun with scattered showers.
In some cases there are many values for the variable, like in a line.
y = 2x + 2 if x is zero x y becomes 2 (0, 2)
if x is 1 y becomes 4 (0,4)
if x is 2 y becomes 6 (0,6)
In other cases there is only one value for the variable but that value is unknown and must be solved for.
10 = 2x + 4 Solving for the variable give x = 3
In a binomial
It is good to make a list of English words and their mathematical translations
less = subtract.
twice = multiply by 2
more than = add that amount to the smaller side or subtract from the larger side.