Y - y1 = m( x - x1); where m = (y2 - y1)/(x2 - x1);
We have m = (6-0)/(7-5) = 6 / 2 = 3 ;
The equation of the line is: y - 0 = 3(x-5);
Finally: y = 3x - 15.
The rate defines how much the portion is of the base.
Ok so we know that y=1 so we can simply sub in the value of y into the equation :
y = -5x +3
1 = -5x +3
Move the -5x to the LHS ( Left-hand-side ) therefore it changes sign as well move 1 to the RHS ( Right-hand-side ) it also changes sign.
5x = 3 - 1
5x = 2
x = 2/5
x = 0.4
Hope this helps :).
Y=4x-5... if you were asking for that in words