Question 4859
Because x-y=1, we can add y to both sides of the equation and get 
x=1+y

Using 2(x)+y=5:
substitute the (1+y)in for x and write the equation:
2(1+y)+y=5

clear the parentheses:
2+2y+y=5

2+3y=5

subtract 2 from both sides:
3y=3

divide both sides by 3
y=1

use x-y=1 to find x
x-(1)=1
x=2

the solution is (2,1)