the slope intercept equation of the line is

y = mx + b,

where m is the slope, b is the y-intercept

the line is parallel to y - 3x = 3

lets write y - 3x = 3 in slope intercept form

y = 3x + 3

the slope of this line is 3

since parallel lines have equal slopes follows m = 3

y = 3x + b

the line goes trough (5,0) that is for x = 5, y = 0

0 = 3*5 + b

b + 15 = 0

b = -15

the slope-intercept equation of the line is

y = 3x - 15