Explain the difference between the union and intersection of two sets.

Union between sets (lets call them A and B) is when all of the elements in set A and B are together. For example, say set A is x, y, z, and set B is l, m, n. A U B would be l, m, n, x, y, z.

Intersection between sets is only for shared elements in each set. For example, if set A is a, b, c, x and set B is  x, y, z, a, then the intersection of sets A and B is a, x

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