Question 262535
we are given
(i) {{{x=y+4}}}
(ii) {{{-x+2y=7}}}
step 1 - where you see x in (ii) put the x stuff from (i) to get
 (iii) {{{-(y+4) + 2y = 7}}}
step 2 - solve for y.
combine like terms on the left to get
(iv) {{{y - 4 = 7}}}
add 4 to get
(v) {{{y = 11}}}
Since y = 11, we can find x as
{{{x = 15}}}
So, our answer is (x,y) = (15,11).