a) I 2x=5-4y
b) II 12y=6x-15
c) I x=2.5-2y
d) II 12y=6(2.5-2y)-15
e) II 12y=15-12y-15
f) II 12y+12y=0
g) II 24y=0
h) II y=0
i) I x=2.5
Now as for A,B, C, D and E:
A) 2y=5 : from h) we get y=0. therefore 2y=0, and 2y=5 is false.
B) 2x=5 : from i) x=2.5. Therefore 2x=5 and this is true
C) y+2x<5: from h,i) y+2x=0+5. 5<5 is false, therefore C is false
D) x+2y>5 : from h,i) x+2y=2.5. 2.5<5, therefore 2.5>5 is false
E) 2y-x>5: from h,i) 2y-x=-2.5. -2.5<5 therefore E is false
