Question

4x-y=7

5x+y=20

Answer 1

4 x - y = 7 Add y to both sides

4 x - y + y = 7 + y

4 x = y + 7 Subtract 7 to both sides

4 x - 7 = y + 7 - 7

4 x - 7 = y

y = 4 x - 7

5 x + y = 20

5 x + 4 x - 7 = 20

9 x - 7 = 20 Add 7 to both sides

9 x - 7 + 7 = 20 + 7

9 x = 27 Divide both sides by 9

9 x / 9 = 27 / 9

x = 3

y = 4 x - 7

y = 4 * 3 - 7

y = 12 - 7

y = 5