Question 295158
"The sum of three numbers is 25. The sum of the first two numbers is 17 less than the third. The third number is 6 more than the second. Find the sum of the second and third numbers." It's a multiple choice answer. (a)4 ,(b)10 ,(c)36 ,(d)15 , and (e)21. The point I'm trying to get across is that the teacher told us the answer, and he said it was (c)36, but I disagree, for the sum of three numbers is 25, so how could two numbers equal 36?

let thenumbers be x. y , z

x+y+z=25
x+y+17= z
z=y+6

x+y+z=17--------------- equation 1
x+y-z=-17--------------  equation 2
z-y=6------------------  equation 3

add equation 2 and equation 3

x+y-z +z-y=-17+6

x=-9

Plug the value of x in equation 1 and equation 2 

-9+y+z=17

-9+y-z=-17

Add these two equations

-18+2y==0
2y=18
y=9

plug the values of x and y in equation1

-9+9+z=25

z=25

x=-9 , y=+9  , z=25

y+z=36.

In your argument you have to remember that there can be negative numbers.

Have fun