the equation of a line in point-slope form is
y - b = m(x - a)
where m is the slope and (a, b) a point on the line
here m = - 2 and (a, b) = (2, 6), hence
y - 6 = - 2(x - 2) ← equation in point-slope form
No it depends on the sum of the two numbers
X - 2y = -10 --> x = 2y -10
3x + 5y = 25 --> 3(2y-10) + 5y = 25 --> 11y - 30 = 25 --> 11y = 55 --> y = 5
x = 2y -10 --> x = 2(5) -10 --> x =10 -10 --> x =0
Answer (0,5)