System of equations.
[tex]\left\{\begin{array}{ccc}y=2x&(1)\\3x+4y=22&(2)\end{array}\right[/tex]
Put (1) to (2):
[tex]3x+4(2x)=22\\3x+8x=22\\11x=22\qquad|\text{divide both sides by 11}\\\boxed{x=2}[/tex]
Substitute the value of x to (1):
[tex]y=2\cdot2\\\boxed{y=4}[/tex]
Solution:
[tex]\huge\boxed{\left\{\begin{array}{ccc}x=2\\y=4\end{array}\right}[/tex]
