System equations
x+10y=36 and 5x+6y=4

So, in the first equation, get x by itself on one side, so you can plug it in to the other equation: x = -10y + 36. Then plug in: 5(-10y + 36) +6y = 4.
Then, distribute and solve for y: -50y + 180 + 6y = 4
                                             = -44y = -176
Divide both sides by -44 to get y by itself.
                                            = y = 4
Then plug in y to the original equation to solve for x.
x + 10(4) = 36
x + 40 = 36
x = -4

So, y = 4, and x = -4

Line ab is y = -7/5x + 56/5i don't understand  where point d comes into this. 

The question of the answer is found in the pic