Step-by-step explanation:
usual line equation :
y = ax + b
a being the slope (the ratio "y coordinate change / x coordinate change" when going from one point on the line to another). and b being the y intercept (the y value when x = 0).
the x intercept is the x value when y = 0.
so,
y = a×0 + b = b
and
0 = ax + b
ax = -b
x = -b/a
b = 5 × -b/a
we have the 2 points (0, b) and (-b/a, 0).
the slope is then (b-0)/(0 - -b/a) = (-5b/a)/(b/a) = -5
to get b we use the given point in the line equation :
y = -5x + b
7 = -5×3 + b = -15 + b
22 = b
so, the full line equation is
y = -5x + 22