Solve {l}{x=-4}{y=5}{z={(x-2y)}-{(2x-5y)}}{text{Solvefor}atext{where}}{a=z}

$$\left. \begin{array} { l } { x = -4 }\\ { y = 5 }\\ { z = {(x - 2 y)} - {(2 x - 5 y)} }\\ { \text{Solve for } a \text{ where} } \\ { a = z } \end{array} \right.$$

Solve for x, y, z, a

$$a=19$$

Solution Steps

Consider the third equation. Insert the known values of variables into the equation.

$$z=-4-2\times 5-\left(2\left(-4\right)-5\times 5\right)$$

Multiply -2 and 5 to get -10.

$$z=-4-10-\left(2\left(-4\right)-5\times 5\right)$$

Subtract 10 from -4 to get -14.

$$z=-14-\left(2\left(-4\right)-5\times 5\right)$$

Do the multiplications.

$$z=-14-\left(-8-25\right)$$

Subtract 25 from -8 to get -33.

$$z=-14-\left(-33\right)$$

Multiply -1 and -33 to get 33.

$$z=-14+33$$

Add -14 and 33 to get 19.

$$z=19$$

Consider the fourth equation. Insert the known values of variables into the equation.

$$a=19$$

The system is now solved.

$$x=-4 y=5 z=19 a=19$$