# How do you solve by substitution #y – 3x = 7# and #21 + 9x = 3y#?

##### 1 Answer

Mar 9, 2018

#### Explanation:

Equation 1:

Substitution : Substitute 7 + 3x for y in the equation 2:

It is true for all real numbers => x can be any real number

Equation 1 and 2 are the same line, and the answers is