The point (x,-1) is a solution of equation 5x+5y=10 and equation 3y=x-6. This means that point satisfy both the equations.
Substitute -1 for x in equation 5x+5y=10 to obtain the value of x.
So the point is (3,-1).
To check
Substitute 3 for x and -1 for y in equation 3y=x-6 to verify the result.
Since point satisfy the equation 3y=x-6 also.
Hence value of x is 3.