Use the following system, use the second equation to make a substitution for x in the first equation
x+5y-10=0
x=2y-8

X in the first equation is given to be equal to 2y - 8. Substituting  this expression for x to the first equation, (2y - 8) +5y - 10 = 0. Solving this gives  y = 2.57. Substituting this value to to any of the equation to get the value of x. Choosing the second equation, 
                                 x = 2 x 2.57 - 8 = -2.86

Thus, the ordered pair for this system is (-2.86, 2.57) 

The answer is 1 because you have to flip the sign when dividing by negative number and 3