To get this answer you would put this information into point-slope form and then solve for the y-intercept
Math Work:
y-y1=m(x-x1) So you would plug in the y1, m and x1
y+7=3(x+1) the negatives cancel out and turn into positives
y+7=3x+3
-7 -7
y=3x-4
negative 4 is your y-intercept (-4)
