Help me please There are 9
9
books stacked on a shelf. The thickness of each book is either 1
1
inch or 2
2
inches. The height of the stack of 9
9
books is 14
14
inches. Which system of equations can be used to determine x
x
, the number of 1
1
-inch-thick books in the stack, and y
y
, the number of 2
2
-inch-thick books?
F. x+y=14x+2y=9
x+y=14x+2y=9

G. x+y=92x+y=14
x+y=92x+y=14

H. x+y=9x+2y=14
x+y=9x+2y=14

J. x+y=142x+y=9
x+y=142x+y=9

Ok here we go ..there are plenty of ways to solve such math problems but we will go for the smartest and easiest ..5x+2y=7  -2x+6y=9we rearrange them into the following ..by multiplying the 1st equation by 2 it becomes 10x + 4y = 14we rearrange it and so it becomes 10x = 14 - 4yas for the second equation we multiply it by 5 and rearrange it so it becomes as to the following ..-10x + 30y = 45rearranging so 10x = 30y -45now 10x equals both 14 - 4y and 30y -45so   14 - 4y = 30y -4531 = 26yy= 31/26 = 1.19 or around 1.2so by now we can calculate x easily as  -2x+6y=9so 2x = 6y -9 = 6 * 31/26 - 9 = -1.84  then x = - 0.92 or around -0.9best luck!