What type of mathematical problem requires a solution?

The choice indicating an equation that asserts a relationship between two expressions is correct because this type of mathematical problem is designed to be solved. An equation typically consists of two expressions set equal to each other, and the goal is to find the value(s) of the variable(s) that satisfy this equality. This solving process usually involves algebraic manipulation to isolate the variable and find a definitive solution.

In contrast, a numerical equation is a specific type of equation, while a polynomial expression is simply a mathematical expression without an equality sign, meaning it does not require a solution on its own. A set of inequalities introduces constraints rather than direct relationships that need to be solved into a single value, often resulting in a range of potential solutions. Thus, the correct answer highlights the fundamental nature of equations in establishing relationships that are open to being explored and solved, which is essential in algebra and higher mathematics.