ANSWER
[tex]x - 3y = - 21[/tex]
EXPLANATION
We want to eliminate the parameter in the equation:
[tex]x = 3t[/tex]
[tex]y = t + 7[/tex]
We just have to make t the subject in any of the equations and substitute into the other.
Let us make t the subject in the second equation to get,
[tex]t = y - 7[/tex]
Put this expression for t in the first equation to get:
[tex]x = 3(y - 7)[/tex]
Expand to obtain:
[tex]x = 3y - 21[/tex]
We rewrite this equation in standard form to get;
[tex]x - 3y = - 21[/tex]
