Solve by substitution method

9x+6y=21-9x+y=35
What is the solution of the method?

Those are two separate equations. You should have typed:

9x + 6y = 21
-9x + y = 35

You can either add them, or SUBSTITUTE y-35 for 9y in the first equation. Either way, you get
7y = 56
y = 8
9x + 48 = 21
x = -3

To solve the given system of equations using the substitution method, we need to solve one equation for one variable and substitute it into the other equation. Let's start by solving the second equation for y.

Rearranging the second equation:
-9x + y = 35
y = 35 + 9x

Now we substitute this expression for y in the first equation:
9x + 6(35 + 9x) = 21

Simplify the equation by distributing:
9x + 210 + 54x = 21

Combine like terms:
63x + 210 = 21

Subtract 210 from both sides:
63x = -189

Divide by 63 to solve for x:
x = -3

Now substitute this value of x back into one of the original equations. Let's use the first equation:
9(-3) + 6y = 21
-27 + 6y = 21

Add 27 to both sides:
6y = 48

Divide by 6 to solve for y:
y = 8

Therefore, the solution to the system of equations is x = -3 and y = 8.