Solve {l}{9x+10=30-x}{b-9x-9=72}

$$\left. \begin{array} { l } { 9 x + 10 = 30 - x } \\ { b - 9 x - 9 = 72 } \end{array} \right.$$

Solve for x, b

$$x=2$$

$$b=99$$

Solution Steps

Consider the first equation. Add x to both sides.

$$9x+10+x=30$$

Combine 9x and x to get 10x.

$$10x+10=30$$

Subtract 10 from both sides.

$$10x=30-10$$

Subtract 10 from 30 to get 20.

$$10x=20$$

Divide both sides by 10.

$$x=\frac{20}{10}$$

Divide 20 by 10 to get 2.

$$x=2$$

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

$$b-9\times 2-9=72$$

Multiply -9 and 2 to get -18.

$$b-18-9=72$$

Subtract 9 from -18 to get -27.

$$b-27=72$$

Add 27 to both sides.

$$b=72+27$$

Add 72 and 27 to get 99.

$$b=99$$

The system is now solved.

$$x=2 b=99$$