find gradient of y plus 2x divide by 4 equal x divide by 3

Do you mean:

y+2x/4 = x/3 or (y+2x)/4 = x/3

y + 2x/4 = x/3
Multiply both sides by 12:
12y + 6x = 4x.
2x + 12y = 0.
m = -A/B = -2/12 = -1/6.

(y+2x)/4 = x/3.
Multiply both sides by 12:
3y + 6x = 4x.
2x + 3y = 0
m = -A/B = -2/3.