3(x+y)-4(x-y)=4

(x+y) of 2+(x-y of 6) =1.

(x+y)/2+(x-y)/6= 1

x/2+x/6+y/2-y/6= 1

2x/3+y/3= 1

2x+y=3 ( 1)

3(x+y)-4(x-y)=4

3x+3y-4x+4y=4

-x+7y=4 (2)

( 1)+2*(2)

y+ 14y= 1 1

y= 1 1/ 15

x=7y-4= 17/ 15

2. Diagonal lines of isosceles trapezoid are perpendicular to each other. If the height of the trapezoid is 5 cm, then the area of the trapezoid is _ 25 _ _.

Because it is an isosceles trapezoid, the diagonal is translated to get an isosceles right triangle. If the height is 5, the length of the hypotenuse is 5X2= 10, that is, upper bottom+lower bottom = 10.

So the area is: 10*5/2=25.