Write in y=mx+b Form x+3y=21

$x + 3 y = 21$

Step 1

The slope-intercept form is $y = m x + b$ , where $m$ is the slope and $b$ is the y-intercept.

$y = m x + b$

Step 2

Rewrite in slope-intercept form.

Subtract $x$ from both sides of the equation.

$3 y = 21 - x$

Divide each term in $3 y = 21 - x$ by $3$ and simplify.

Divide each term in $3 y = 21 - x$ by $3$ .

$\frac{3 y}{3} = \frac{21}{3} + \frac{- x}{3}$

Simplify the left side.

Cancel the common factor of $3$ .

Cancel the common factor.

$\frac{3 y}{3} = \frac{21}{3} + \frac{- x}{3}$

Divide $y$ by $1$ .

$y = \frac{21}{3} + \frac{- x}{3}$

Simplify the right side.

Simplify each term.

Divide $21$ by $3$ .

$y = 7 + \frac{- x}{3}$

Move the negative in front of the fraction.

$y = 7 - \frac{x}{3}$

Write in $y = m x + b$ form.

Reorder $7$ and $- \frac{x}{3}$ .

$y = - \frac{x}{3} + 7$

Reorder terms.

$y = - (\frac{1}{3} x) + 7$

Remove parentheses.

$y = - \frac{1}{3} x + 7$