if two distinct lines intersect, which must be true?
a) the lines are parallel
b) the lines are perpendicular
c) the lines form angles at the intersection
d) the lines form right angles at the intersection

I would say C

Step-by-step explanation:

the lines are intersection so the lines are going to form some angles like an obtuse angle, right angle or acute

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18