I need help with this problem I'm not that good in math

1/5(15x-20) = 1/3(12x-9)
multiply the 15 and 20 on the left by 1/5 to get
3x-4
now multiply 12 and 9 by 1/3 to get
4x-3
now you have 3x-4 =4x-3
now solve for x
3x-4 =4x-3
subtract 3 x from each side:
-4 = x-3
add 3 to each side
-1 = x
x = -1