Question

Solve the simultaneous equations
x + 7y = 15
x + 2y = 5

Answer 1

x + 7y = 15
x + 2y = 5
———————————
x + 7y = 15
(x + 2y = 5) -1
———————————
x + 7y = 15
-x - 2y = -5
———————————
x + 7y = 15
+ -x - 2y = -5
——————
0 + 5y = 10
———————————
5y = 10
— —
5 5
———————————
y = 2
Plug Y into one of the original equations to find x
———————————
x + 2y = 5
———————————
x + 2(2) = 5
———————————
x + 4 = 5
———————————
x + 4 = 5
- 4 | - 4
———————————
x = 5 - 4
———————————
x = 1
———————————


Answer is:
y = 2, x = 1
Or
(1, 2)

Answer 2

x=1, y=2

Explanation:

x + 7y = 15

x + 2y = 5

Subtract the two equations

x + 7y = 15

-x - 2y =- 5

------------------------

0x +5y = 10

Divide by 5

5y/5 = 10/5

y =2

Now find x

x+2y = 5

x +2(2) = 5

x +4 = 5

Subtract 4 from each side

x-4+4 = 5-4

x = 1