Solve using substitution x=y+3. 2x-y=5

X = y + 3
2x - y = 5

substitute the first equation into the second equation;
2x - y = 5
2(y + 3) - y = 5
2y + 6 - y = 5
y + 6 = 5

solve for y;
y + 6 = 5
y = 5 - 6
y = -1

solve for x;
x = y + 3
x = -1 + 3
x = 2

x = 2, y = -1

hope this helped, God bless!