Starting with the first expression:
[tex]\begin{gathered} (x^2-6x+7)-(x^2-14x+13) \\ \Rightarrow x^2-6x+7+x^2+14x-13 \\ \text{collect like-terms} \\ x^2+x^2-6x+14x-13+7 \\ \Rightarrow2x^2+8x-6 \\ \\ \text{This is not the answer, as it is not the same with the two(2) expressions given in the solution} \end{gathered}[/tex]Simplifying the second expression:
[tex]\begin{gathered} 2(x^2-4x)+5(x+1) \\ \Rightarrow2x^2-8x+5x+5 \\ \Rightarrow2x^2-3x+5 \\ \\ \text{This expression is equal to the option B} \end{gathered}[/tex]Simplifying the third expression:
[tex]\begin{gathered} x(2x+1)-(4x-5)_{} \\ \Rightarrow2x^2+x-4x+5 \\ \Rightarrow2x^2-3x+5 \\ \\ \text{This expression is also equal to option B} \end{gathered}[/tex]Simplifying the fourth expression:
[tex]\begin{gathered} x(3x-4)-3(x^2+2)+12x \\ \Rightarrow3x^2-4x-3x^2-6+12x \\ \Rightarrow3x^2-3x^2-4x+12x-6 \\ \Rightarrow8x-6 \\ \\ \text{This is correct for option A} \end{gathered}[/tex]Simplifying the last expression:
[tex]\begin{gathered} x(x+1)+x(x+1)-4(x^2-1.5x)+2(x^2-3) \\ \Rightarrow x^2+x+x^2+x-4x^2+6x+2x^2-6 \\ \Rightarrow x^2+x^2-4x^2+2x^2+x+x+6x-6 \\ \Rightarrow8x-6 \\ \\ \text{This expression is also true for option A} \end{gathered}[/tex]