Which value of x satisfies both -9x + 4y = 8 and -3x − y = 4 given the same value of y?

-9x+4y=8 (equation. 1)

-3x-4=4. (equation 2)

(1) + (2)

-12x+3y=12

-4x+y=4

y=4+4x (3)

substitute y value in eq (1)

-9x+4(4+4x)=8

-9x+16+16x =8

7x+16=8

7x=-8

x=-8/7

therefore substitute x in eq (3)

y=4+4(-8/7)

y=4-32/7 = 28-32/7

y= -4/7

x=-8/7, y=-4/7.

answer: all of the odd numbers were opened

the first person was the one that was opening all of the lockers. since one is odd, this causes all of the odd number lockers to be opened in the end.