Explanation:
In order to solve this problem, we'll use the concept of Mid-segment of a Trapezoid which is defined as the segment that connects he midpoints of the two non-parallel sides of the trapezoid. So, it is true that:
[tex]EF=\frac{AD+BC}{2} \\ \\ 5x=\frac{x+2+43}{2} \\ \\ Isolating \ x: \\ \\ 10x=x+45 \\ \\ 9x=45 \\ \\ x=5 \\ \\ \\ So: \\ \\ EF=5x \\ \\ EF=5(5) \\ \\ \boxed{EF=25}[/tex]
