4. $\frac{n - 4}{6}=\frac{n - 7}{9}$

Explanation:

Step1: Cross - multiply

$9(n - 4)=6(n - 7)$

Step2: Expand both sides

$9n-36 = 6n-42$

Step3: Move terms with n to one side

$9n - 6n=-42 + 36$

Step4: Simplify

$3n=-6$

Step5: Solve for n

$n=-2$

Answer:

$n = - 2$