Please help solve these simultaneous linear equations.

Question

3x + y = 18
2x – y = 7



5x + 3y = 21
2x + 7y = 20



5x + 3y = 31
2x + y = 12



2x + 3y = 1
-x + 2y = -4



7x + 2y = 17
2x – 2y = 1

Answer 1

Carin,

3x + y = 18
2x – y = 7      If you add the two equations you will just have 5x + 0 = 25, x = 5 and 2(5) - y = 7, y = 3

You can repeat the same for
7x + 2y = 17
2x – 2y = 1

And for

5x + 3y = 21
2x + 7y = 20 multiply the first by -2 and the second by 5 and just add them up. you should get

-10x    - 6y =  -42

 10x + 35y  = 100

0 + 29y = 58, => y = 2 and  5x + 3(2) = 21, => x = ........

I hope this helps