To find the slope from an equation, solve the equation for y.
The equation will have the form y = mx + b, called the slope-intercept form.
Then m = slope.
Let's solve your equation for y.
![2x + 7y = 21](https://img.qammunity.org/2019/formulas/mathematics/middle-school/w729cwq970xnyefxzj9g2fdy2bwgvc8dty.png)
Subtract 2x from both sides.
![7y = -2x + 21](https://img.qammunity.org/2019/formulas/mathematics/middle-school/94k0xbc59mk3kiszeg9u6yopynz42nbia0.png)
Divide both sides by 7.
![y = -(2)/(7) x + (21)/(7)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/mcg7ikizwdhpl3xni37pv6xxdqa29a4492.png)
![y = -(2)/(7) x + 3](https://img.qammunity.org/2019/formulas/mathematics/middle-school/ss59xnjehgxhedn811ie02cb148vfhn6ya.png)
Now compare the equation above to y = mx + b.
m is the number that multiplies x, and it is the slope.
![m = -(2)/(7)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/yfsm4ntf364jzaiwrtnmb876oxotsgb764.png)