Solve {l}{x-a=7}{2x+y+2a=4}

$$\left\{ \begin{array} { l } { x - a = 7 } \\ { 2 x + y + 2 a = 4 } \end{array} \right.$$

Solve for x, y

$$x=a+7$$

$$y=-4a-10$$

Steps Using Substitution

To solve a pair of equations using substitution, first solve one of the equations for one of the variables. Then substitute the result for that variable in the other equation.

$$x-a=7,2x+y+2a=4$$

Pick one of the two equations which is more simple to solve for x by isolating x on the left hand side of the equal sign.

$$x-a=7$$

Add a to both sides of the equation.

$$x=a+7$$

Substitute a+7 for x in the other equation, 2x+y+2a=4.

$$2\left(a+7\right)+y+2a=4$$

Multiply 2 times a+7.

$$2a+14+y+2a=4$$

Add 14+2a to 2a.

$$y+4a+14=4$$

Subtract 14+4a from both sides of the equation.

$$y=-4a-10$$

The system is now solved.

$$x=a+7,y=-4a-10$$