Final answer:
By applying the Subtraction Property of Equality to the equation PQ + ST = RS + ST, and subtracting ST from both sides, we find that the correct answer is PQ = RS.
Step-by-step explanation:
The Subtraction Property of Equality is a fundamental concept in algebra, asserting that subtracting the same quantity from both sides of an equation preserves equality. In the equation PQ+ST=RS+ST, applying the Subtraction Property involves subtracting ST from both sides. This action eliminates the ST terms on both sides, leaving us with PQ=RS. The equality is maintained, and we have successfully simplified the equation. This property is crucial in algebraic manipulations, allowing for the isolation of variables and the simplification of expressions by removing common terms from both sides of an equation.