`x+y = 10->(1)`
`2x+y = 18->(2)`
`4x-3y = 26->(3)`
Subtracting (2) from (1),
`2x+y-x-y = 18-10=> x = 8`
`y = 10-8 =>y= 2`
Now, multiplying (1) with 3 and then adding (1) and (3),
`3x+3y +4x-3y = 30+26`
`7x = 56=> x = 8`
`y = 10-8 =>y = 2`
Now, multiplying (2) with 3 and then adding (2) and (3),
`6x+3y+4x-3y = 54+26 =>10x = 80=> x = 8`
`y = 18-16 = 2`
So, solving all three equations, we get,
`x=8` and `y = 2`
So, solution for these three equations is unique solution.