We can do this as follows: (Note: In copying the LaTeX from Tekmaker and pasting it here the third equation has been renumbered to (1)!!!. The third equation below should be numbered (3), of course.)
Let's first rewrite the two given equations as: \begin{equation} y1 = -\frac{3}{2}x+\frac{5}{2} \end{equation} \begin{equation} y2 = -4x+5 \end{equation}
andthelineperpendiculartothefirstoftheaboveas:y3=mx+cwhere$m$isitsgradientand$c$isitsintersectionwiththey−axis.
Thegradient,$m$,isgivenby−1/thegradientofthelinetowhichitisperpendicular,so$m=23$Tofindthepointofintersectionoflines(1)and(2)weneedtoequatethem: -\frac{3}{2}x+\frac{5}{2}=-4x+5andsolvefor$x$.Thisisstraightforwardandresultsin$x=1$.Pluggingthisbackineitherequation(1)orequation(2)wefindthatthevalueofyattheintersectionpointisalso$y=1$Nowweputtheknownvaluesof$x$and$y$attheintersectionpoint,togetherwithourvaluefor$m$intoequation(3): 1=\frac{2}{3}*1+c$$
fromwhichweget$c=13$;so,usingequation(3),wegettheequationoftheperpendicularlineas: y3=\frac{2}{3}x+\frac{1}{3}
Let's plot a graph to see if the result looks sensible: