Question

Which of the following is a solution of the system 2x + y = 9 and 3x + 5y = 19.​

Answer 1

2x+y=9

3x+5y=19

I will do this problem in 2 ways. I.)Substitution II.)Elimination

Solution I.) Substitution

We can subtract 2x from both sides in the first equation.

y=9-2x

Now we can substitute the y in the second equation with 9-2x

3x+5(9-2x)=19

-7x+45=19

-7x=-26

x=26/7

y=9-2(26/7)=11/7

Solution II.)Elimination

We can multiply both side of first equation by 5 to get a 5y in both equations.

10x+5y=45

Now because both are positive 5y we just need to do simple subtraction of the 2 equation, each side respectively.

(10x+5y)-(3x+5y)=45-19

7x=26

x=26/7

2*26/7+y=9

y=11/7

Ultimately you get the same answer, both are viable methods, some problems are faster with one method but I recommend mastering both since they are very useful.