How do you solve $y=x+3$ and y= 2x using substitution ?

Hint: The given system of equation is linear equation in 2 variables so we can find the value of both variable x and y using these 2 equations, in substitution method we find the value of one variable in terms of other variable from the first equation and put it in the second equation.

Complete step by step answer:
The given system of equation is $y=x+3$ …eq1 and y =2x ….eq2
We can see that the value of y is equal to 2x from eq2
So we can replace y with 2x in eq1
So we can write $2x=x+3$ …. eq3
Now it became a one variable linear equation
Subtracting x from LHS and RHS in eq3 we get
x = 3
So the value of x is equal to 3
From the first equation we can see that y is equal to x + 3
So the value of y is equal to 3+3 which is equal to 6
The solution to the system of equation is y = 6 and x= 3

Note:
We can check whether our answers are correct or not by putting the value of x and y in both the equations. If the answers do not satisfy one of the equations then the answer is wrong.
If we put y = 6 and x= 3 in $y=x+3$ we will get 6=3+3 which is correct, if we put y = 6 and x= 3 in y=2x then we will get $6=2\times 3$ which is also correct. So the answer is satisfying both the equations so it is the correct answer.