Question 391287
x-y=21_x+y=185

Since -y does not contain the variable to solve for, move it to the right-hand side of the equation by adding y to both sides.
x=y+21_x+y=185

Replace all occurrences of x with the solution found by solving the last equation for x.  In this case, the value substituted is y+21.
x=y+21_(y+21)+y=185

Remove the parentheses around the expression y+21.
x=y+21_y+21+y=185

Since y and y are like terms, add y to y to get 2y.
x=y+21_2y+21=185

Since 21 does not contain the variable to solve for, move it to the right-hand side of the equation by subtracting 21 from both sides.
x=y+21_2y=-21+185

Add 185 to -21 to get 164.
x=y+21_2y=164

Divide each term in the equation by 2.
x=y+21_(2y)/(2)=(164)/(2)

Simplify the left-hand side of the equation by canceling the common factors.
x=y+21_y=(164)/(2)

Simplify the right-hand side of the equation by simplifying each term.
x=y+21_y=82

Replace all occurrences of y with the solution found by solving the last equation for y.  In this case, the value substituted is 82.
x=(82)+21_y=82

Remove the parentheses around the expression 82.
x=82+21_y=82

Add 21 to 82 to get 103.
x=103_y=82

This is the solution to the system of equations.
x=103_y=82