Question

if 4x+5y=10 and 5x+4y=17,then the value of x-y is:
A-5
B-7
C-9
D-11​

Answer 1

Answer:

B )7

Step-by-step explanation:

4x+5y=10  (*5)  ===>        20x + 25y = 50

5x+4y=17   (*- 4) ====>  - 20x -  16y  = -68  

                                     -------------------------

( add them together)        0 + 9y= -18  ======> y= -2

4x + 5(-2)=10

 4x -10 =10

4x =20

x=20/4

x=5

x=5

y=-2

x- y= 5- (-2) =7