$\"\"$

The sentence is “twice the sum of s and t decreased by s”.

The word “sum” represents the symbol +.

The word “decreased” represents the symbol $\"\"$ .

$\"\"$

The algebraic expression is $\"\"$

$\"\"$

$\"\"$ (Distributive Property: a (b + c) = ab + ac)

$\"\"$ (Simplify)

$\"\"$ (Commutative Property: a + b = b + a)

$\"\"$

$\"\"$ (Associative Property: (a + b) +c = a + (b + c))

$\"\"$ (Distributive property: a (b + c) = ab + ac)

$\"\"$ (Subtract: $\"\"$ )

$\"\"$

The simplified expression is $\"\"$ .