Question

solve the simultaneous equation x+y=4;2x-5y=1

Answer 1

x+y =4
x = 4-y

2x -5y =1
2(4-y) -5y =1
8-2y-5y =1
-7y = 1-8
7y = 7
y =1

x = 4-(1)
x = 3
so y = 1. and x = 3.

Answer 2

x+y=4
2x-5y=1
=>x+y=4]*2
     2x-5y=1]*1
=>2x+2y=8
     2x-5y=1
On subtracting we get,
     =0x+7y=7
        =>y=7/7
            y=1
Substitute y's value in any one of the equation,
x+1=4
=>x=4-1
=>x=3