Which step is the same in the construction of a perpendicular line through a point on a line and the construction of a perpendicular line through a point off a line? Create only one arc on the original line.
Create two arcs on the original line.
Place the compass on only one point off the original line.
Place the compass on only one point on the original line.

Step-by-step explanation:

Create two arcs on the original line.

Place the compass on two points on the original line, one after another for marking a point.

make a line from the original point on the line to the marked point (MP)

the sketch as attached

Ok here we go ..there are plenty of ways to solve such math problems but we will go for the smartest and easiest ..5x+2y=7  -2x+6y=9we rearrange them into the following ..by multiplying the 1st equation by 2 it becomes 10x + 4y = 14we rearrange it and so it becomes 10x = 14 - 4yas for the second equation we multiply it by 5 and rearrange it so it becomes as to the following ..-10x + 30y = 45rearranging so 10x = 30y -45now 10x equals both 14 - 4y and 30y -45so   14 - 4y = 30y -4531 = 26yy= 31/26 = 1.19 or around 1.2so by now we can calculate x easily as  -2x+6y=9so 2x = 6y -9 = 6 * 31/26 - 9 = -1.84  then x = - 0.92 or around -0.9best luck!