Question

ABCD is a cyclic quadilateral .If angle A=(4y+20°),angle B=(3y-5)° ,angle C=(-4x°,angle D=(-7x+5)°. Find x &y.

Answer 1

4y + 20 - 4x = 180      =      x - y = -40
3y - 5 - 7x +5 = 180    =      7x -3y = 180


by elimination method

y = 115
x =  75

Answer 2

Opp sides of cyclic quadrilateral is 180°.

Now,
4y+20°-4x=180° -1
and
3y-5°-7x+5°=180°_2
In 1,
4y-4x=160°
In 2,
3y-7x=180°
Multiplying 3 by 3 and 4 by 4,
12y-12x=480°
12y-28x=720°
Sub 4 from 3 ,
16x=240°
x=15°
Put value of x in 1 ,
4y-60°=160°
4y=220°
y=55°