Question

-15x+7y=1

3x-y=1

Answer 1

Problem: -15x+7y=1 3x-y=1
-15x+7y=1
3x-y=1

1) -15x + 7y = 1
2) 3x - y = 1

Solve equation 2 for y.

3x - y = 1
-y = -3x + 1
y = 3x - 1

Substitute that into equation 1.

-15x + 7y = 1
-15x + 7(3x - 1) = 1
-15x + 21x - 7 = 1
6x - 7 = 1
6x = 8
x = 8/6
x = 4/3

Use that in equation 2 to solve for y.

3x - y = 1
3(4/3) - y = 1
4 - y = 1
4 - y - 4 = 1 - 4
-y = -3
y = 3

Use equation 1 to verify.

-15x + 7y = 1
-15(4/3) + 7(3) = 1
-20 + 21 = 1
1 = 1

Answer: x = 4/3, y = 3