Answer: y = x + 7
Explanation:
To find the slope-intercept form (y=mx+c), we have to make 'y' the subject of the equation:
3y - 3x = 21 [add 3x to both sides]
3y = 3x + 21 [divide all terms by 3]
y = x + 7
∴ 3y - 3x = 21 in slope-intercept form is y = x + 7.