[Mr. K]

C would not wor

5x - y = 5
7x - 3y = -1

Line 1 time -3

-15x +3y = -15
7x _3Y = -1

Add them

-8X = -16

x = 2

so....

5x - y = 5
7x - 3y = -1

5(2) - y = 5
7(2) - 3y = -1

10 -y = 5 (subtract 5 from both sides, and add y to both)
14 -3y = -1 ( add 1 to each side and ad 3y to each side)

10 -5 = y
14 + 1 = 3y

5 = y
15 = 3y

x = 2
y = 5

CHECK: (ALWAYS DO THIS!!!!!!!!!!!!!!!)
5x - y = 5
7x - 3y = -1

5(2) - 5 = 5
7(2) - 3(5) = -1

10 - 5 = 5 (correct)
14 - 15 = -1 (correct)

[Bob]

The solution to the set of equations is x = 2, y = 5.

Multiplying equation #1 by either -3 or 3 will give you two equations that (by adding or subtracting) will result in either:

8x = 16

or

-8x = -16

In either case, x equals 2.