By standard form do you mean slope intercept?
The equation of a line with x-intercept b and slope m is given by:
y = m(x - b)
Substitute m=3 and b=-2:
y = 3(x - (-2))
= 3(x + 2)
= 3x + 6
Therefore, the equation of a line with slope 3 and x-intercept -2 is:
y = 32 + 6