Solve this system of equations: 2x+y=11
y=x-1
explain how you got it and try to explain your steps!

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

y = 3 and x = 4

It would be 18 cm