Given points are (h, 3) and (4, 1). ∴ Slope of the line joining (h, 3) & (4, 1) = $\frac{1-3}{4-h}$ = $\frac{-2}{4-h}$ ... (i) slope of given line 7x – 9y – 19 = 0 is $\frac{7}{9}$ ... (ii) If two lines intersect at right angles, then (slope of (i)) × (slope of (ii)) = –1 $\left(\frac{-2}{4-h}\right)$ × $\left(\frac{7}{9}\right)$ = - 1 ⇒ $\frac{-14}{36-9h}$ = - 1 ⇒ 14 = 36 - 9h ⇒ 9h = 36 - 14 ⇒ 9h = 22 ⇒ h = $\frac{22}{9}$