well use the substitution method u make x the subject .. on the ... 2nd equation because it is easier so x=2+y and put it into the other one so whenevery you see an x replace it with 2+y so x+2y=17= (2+y)+2y=17
then~ you collect like terms
2+3y=17 (minus 2 on both sides)
3y=15 ( divide by 3 on both sides)
y=5 ( we are still not done no to find x) put this into the 2nd equation so
x-5=2 therefore x=7
now you cheak and put them back into the equation and see if it makes sense
(7)+2(5)=17
7+10=17 ( it is correct)~ tada^______^ done~^^