Explanation:
from what I can see, the line goes through (100, 0) and (0, -100).
the general line function is
y = ax + b
a is the slope of the line, excised as ratio y/x, as it indicates how many units y changes, when x changes a certain amount of units.
we use the 2 points to find the coordinate differences and therefore the slope.
going from (0, -100) to (100, 0) x changes by +100, and y changes by +100.
so, the ratio y/x = a = 100/100 = 1
now to find b we use the coordinates of one of the points in the main equation and solve for b. we use e.g. (100, 0)
0 = 1×100 + b
b = -100
so, the line function is
y = x - 100