Me. is (3,13) a solution of the equation y=4x?

Well I don't know.  Let's find out.

When you say  (3,13),  that means  'x'  is  3  and  'y'  is  13.
We'll plug those into the equation, and see if the equation is a true statement.

y = 4x

13 = 4 (3)

4 (3)  means  4 x 3,  and that's  12.

So the equation says    13 = 12 .

Is that a true statement ?
I don't think so.

So  (3, 13)  is NOT a solution of      y = 4x