Final answer:
The question is missing specific details required to solve for x in the context of parallel lines and a transversal. Without additional information or a clear diagram, the calculation for x cannot be accurately completed.
Step-by-step explanation:
From the question, it appears that m and n are parallel lines, and we're dealing with alternate interior angles or corresponding angles created by a transversal t.
However, the provided details do not give a specific enough context to form a clear picture of the geometric scenario.
The typical approach when given parallel lines and a transversal is to set the expressions for the alternate interior angles equal to each other if the problem implies they are congruent, which is often the case with parallel lines. Unfortunately, without a clear geometry problem or diagram, we cannot solve for x.
If a specific equation or more clarity was provided, such as 'm angle n equals t angle', we would use that information to set up an equation and solve for x. Assuming the angles given by (4x + 3) degrees and (x - 3) degrees are either alternate interior angles or corresponding angles, we could solve for x by setting 4x + 3 = x - 3 and simplifying.