How to solve this please

-x+y=12
x+2y=3

these are simultaneous equation, u can solve them by addition

-x+y=12
x+2y=3

add the two equations, the x will cancel out and you'll have

3y=15
y=5

substitute the value of y in any of the original equations
-x+5=12
-x=7
x=-7

note: these equations are simple and the x was ready to cancel out, if u have more difficult equations, try to get rid of either x or y by changing the sign of any of the equations or multiply it with a suitable number.


another way to solve these equations is by substitution
e.g. from ur first equation, y=12+x
substitute the value of y in the second equation and u'll have
x+2(12+x)=3
x+24+2x=3
3x= -21
x=-7

then substitute the value of x in any of the equations and u'll get y=5

Because you have a -1x and a 1x, when you add these together you will get 0 which will only leave 3y=15. From here we can divide by 3 to solve for y and we get y=5. When we plug this in for y we get -x+5=12. Subtract 5 and then divide by -1 to solve for x and we get x to be -7

y=5
x=-7

Hello

Add both equations. Then x will disappear

- x + y + x + 2y = 12 + 3
3y = 15
y = 15/3 = 5

now take back the first equation, and plug your solution for y

- x + 5 = 12
- x = 12 - 5 = 7
x = - 7

Hope it helps

Bye !

-x+y=12 (1)
x+2y=3 (2)

Let's add (1) and (2) member to member.
3y=15
y=5

Let's put it in (1).
-x+5=12
x=5-12
x=-7

The system of equations has got an unique solution.
x=-7
y=5

Add to obtain:-
3y = 15
y = 5

x + 10 = 3
x = - 7

x = - 7 , y = 5

-x+y=12
x+2y=3
--------------
0x+3y= 15
y= 15/3
y= 5<------

put y=5 in any one of that

x+2(5)= 3
x+10= 3
x= -7<---------