Question

Solve this system of equations: 2x+y=11

Answer 1

Use the substitution method to solve. 

2x+y=11
y=x-1

We have the value for y, so put it in the first equation.

2x + x - 1 = 11
2x + x = 3x
3x - 1 = 11
      + 1    +1

3x = 12
x = 4

Now solve for y 

y=x-1
y = 4 - 1
y = 3

Answer: y = 3 and x = 4

Answer 2

1) Solve for y in 2x+y=11

⇒ Subtract 2x from both sides

y=11−2x

2) Start with the original equation 
y=x−1

⇒ Let y=11−2x
11−2x=x−1 

3) Solve for x in 11−2x=x−1

⇒Solve for x
11−2x=x−1

⇒ Add 2x to both sides
11=x−1+2x

⇒Gather like terms
11=(x+2x)−1

⇒ Simplify (x+2x)−1 to 3x−1
11=3x−1

⇒Add 1 to both sides
11+1=3x

⇒Simplify 11+1 to 12
12=3x

⇒Divide both sides by 3
12/3=x

⇒Simplify 12/3 to 4
4=x

⇒ Switch sides
x=4


4) Substitute x=4 into y=11−2x

⇒Start with the original equation 
y=11−2x

⇒Let x=4
y=11−2×4

⇒Simplify
y=3

YOU GET 

x=4 
y=3