Question

If 15x + 17 y = 21 and 17x + 15y = 11 Then find the value of x+y.​

Answer 1

15x+17y=21-------eq 1
17x+15y=11-------eq 2
Adding eq 1 and 2
15x+17y=21
+17x+15y=11
__________
32x+32y=32
Dividing both side by 32
x+y=1

Answer 2

15x+17y=21 .....(1)
17x+15y=11 .....(2)
17×eqn(1)−15× eqn(2) gives
255x+289y−255x−225y=357−165
⇒64y=192
⇒y=
64
192
​
=3
Substitute the value of y=3 in (1) we get
15x+17×3=21
⇒15x=21−51=−30
∴x=
15
−30
​
=−2
Hence x=−2,y=3
And x+y=−2+3=1