the slope and intercept form of a straight line equation is y = mx + c
where m - slope of the line
c - intercept i.e the distance between the origin and the point at which the line intercepted on the y axis
give that x = 30
y = 50
m = 2.5
plug in the values of x, y and m in y = mx + c
we get 50 = 2.5 *30 + c
solving for c, we get c = - 25
option c is the right answer