Solve by substitution 3x+y=3 and 7x+2y=1

3x + y = 3

7x + 2y = 1

First isolate one of the variables (x or y) in one of the equations.

Isolate "y" in the first equation(because it is the easiest to isolate) and substitute it into the second equation.

3x + y = 3      Subtract 3x on both sides

3x - 3x + y = 3 - 3x

y = 3 - 3x

7x + 2y = 1

7x + 2(3 - 3x) = 1     [since y = 3 - 3x, you can substitute (3-3x) for "y"]

Multiply/distribute 2 into (3 - 3x)

7x + (3(2) - 3x(2)) = 1

7x + 6 - 6x = 1

x + 6 = 1     Subtract 6 on both sides

x = -5

Now that you know "x", substitute it into one of the equations (I will do both)

3x + y = 3

3(-5) + y = 3       [since x = -5, you can plug in -5 for "x"]

-15 + y = 3    Add 15 on both sides

y = 18

7x + 2y = 1

7(-5) + 2y = 1

-35 + 2y = 1     Add 35 on both sides

2y = 36     Divide 2 on both sides

y = 18

x = -5, y = 18  or  (-5, 18)

i think it is everything has to equal 180 so, if i correct 4=c. 6=d. 8=a. 7=b. and the last question would be c. because they are parallel lines and they are congruent.

step-by-step explanation:

the reason everything has to equal to 180 is because that is how it works. i'm guessing that is its rule. 4 and 8 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 6 and 7 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 60+60 is 180. so, now you have your answer

that is the sum

step-by-step explanation:

there are no other answers without knowing the variables values