solve the following systems algebraically
a. x+2y=17
x-y=2

There are 3 methods to solve this. elimination substitution and graphing but i am going to use the elimination method.
  x+2y=17
  x-y   =2
0+3y  =15   ( subtracted down to eliminate the x)( x-x=0, 2y-(-y)=3y, and 17-2=15)
     3y=15    (divide both sides by 3 to solve for y)
      y=5
substitute the y=5 in any of the above equations and solve for x
ie... ( meaning where you find y in the equation, u replace it with a 5)

it will be easier to solve for x in (x-y=2) so i will use that one.
x-(5)=2  ( add 5 on both sides to solve for x)
x=7

10.4 is the answer for you